From 1a8b22cb4f51b6302e1411ecd94851270fd42eaf Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Thu, 22 Aug 2013 15:26:26 -0500 Subject: Add while loop to bash --- bash.html.markdown | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/bash.html.markdown b/bash.html.markdown index 7421f880..1473e669 100644 --- a/bash.html.markdown +++ b/bash.html.markdown @@ -53,6 +53,13 @@ else echo "And this is not" fi +# And the usual while loop: +while [true] +do + echo "put loop content here..." + break +done + # Expressions are denoted with the following format: echo $(( 10 + 5 )) -- cgit v1.2.3 From 58cd4b274f4ef6dce15bf30eccad4691aaf835ed Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 09:50:13 -0500 Subject: add special characters to c --- c.html.markdown | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/c.html.markdown b/c.html.markdown index 24a96463..c8c3e33b 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -20,6 +20,12 @@ memory management and C will take you as far as you need to go. Multi-line comments look like this. They work in C89 as well. */ +//Special characters: +'\n' // newline character +'\t' // tab character +'\b' // backspace character +'\0' // null character + // Import headers with #include #include #include -- cgit v1.2.3 From deaaf3412d01a69fdc4354564fba5506ef65f4c8 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 10:51:48 -0500 Subject: Add print formatting characters --- c.html.markdown | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/c.html.markdown b/c.html.markdown index c8c3e33b..a9fd8e50 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -23,9 +23,22 @@ Multi-line comments look like this. They work in C89 as well. //Special characters: '\n' // newline character '\t' // tab character +'\v' // vertical tab +'\f' // new page +'\r' // carriage return '\b' // backspace character '\0' // null character +//print formatting: +"%d" // integer +"%3d" // minimum length of 3 digits for integer (right justifies text) +"%s" // string +"%f" // float +"%3.2f" // minimum 3 digits left and 2 digits right decimal float +"%7.4s" // (can do with strings too) +"%c" // char +"%p" // pointer + // Import headers with #include #include #include -- cgit v1.2.3 From e03cda583dd6127831a32fcc8bd8cd8b53399794 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 11:44:45 -0500 Subject: Add more to string formatting. --- c.html.markdown | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/c.html.markdown b/c.html.markdown index a9fd8e50..4e1e1e56 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -22,7 +22,7 @@ Multi-line comments look like this. They work in C89 as well. //Special characters: '\n' // newline character -'\t' // tab character +'\t' // tab character (left justifies text) '\v' // vertical tab '\f' // new page '\r' // carriage return @@ -38,6 +38,12 @@ Multi-line comments look like this. They work in C89 as well. "%7.4s" // (can do with strings too) "%c" // char "%p" // pointer +"%x" // hexidecimal +"%o" // octal +"%%" // prints % + +// Constants: use #define keyword, no semicolon at end. +#define DAYS_IN_YEAR = 365 // Import headers with #include #include -- cgit v1.2.3 From dba7ec8b9643f693bdb023f9827999b2b14d008b Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 12:50:58 -0500 Subject: Add getchar(), putchar(), EOF to C --- c.html.markdown | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/c.html.markdown b/c.html.markdown index 4e1e1e56..7010b9d5 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -427,6 +427,16 @@ void str_reverse(char *str_in) } } +// Built in functions: +// from stdio.h: +int c = getchar(); //reads character from user. If user types hello, only h is read. +// getchar() can be stored into int or char. I am using int because char is not large +// enough to store EOF used below. +while (c != EOF) { // EOF is value for "end of file". Linux: CTRL+D, Windows: CTRL+X + putchar(c); //prints character (without newline at end) + char c = getchar(); +} + /* char c[] = "This is a test."; str_reverse(c); -- cgit v1.2.3 From f1b1fd8e2efd6c30e553aae1c4f6cc28a6554e8f Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 13:06:37 -0500 Subject: Add clarity to EOF. Add %ld for longs in C --- c.html.markdown | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index 7010b9d5..869ab984 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -34,6 +34,7 @@ Multi-line comments look like this. They work in C89 as well. "%3d" // minimum length of 3 digits for integer (right justifies text) "%s" // string "%f" // float +"%ld" // long "%3.2f" // minimum 3 digits left and 2 digits right decimal float "%7.4s" // (can do with strings too) "%c" // char @@ -429,10 +430,12 @@ void str_reverse(char *str_in) // Built in functions: // from stdio.h: -int c = getchar(); //reads character from user. If user types hello, only h is read. -// getchar() can be stored into int or char. I am using int because char is not large -// enough to store EOF used below. -while (c != EOF) { // EOF is value for "end of file". Linux: CTRL+D, Windows: CTRL+X +int c = getchar(); //reads character from input. If input = hi, only h is read. +// getchar() can be stored into int or char. I am using int because +// char is not large enough to store EOF used below. +while ((c = getchar()) != EOF) { // EOF constant "end of file". + // Linux: CTRL+D, Windows: CTRL+X + // must have () around getchar() as != is run before =. putchar(c); //prints character (without newline at end) char c = getchar(); } -- cgit v1.2.3 From b0c5ca0a1cc5a62fc8569fffffcdf35bf44e8dc8 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 15:57:18 -0500 Subject: Add note about loops C --- c.html.markdown | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/c.html.markdown b/c.html.markdown index 869ab984..166c43e6 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -231,6 +231,12 @@ int main() { printf("I print\n"); } + // Notes: + // Loops MUST always have a body. If no body is needed, do this: + for (i = 0; i <= 5; i++) { + ; // use semicolon to act as the body (null statement) + } + // While loops exist int ii = 0; while (ii < 10) { -- cgit v1.2.3 From 5c711eb30fe8cd810627742a30c016f458bd773c Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 16:24:56 -0500 Subject: Add more shorthand notes, array notes to C --- c.html.markdown | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/c.html.markdown b/c.html.markdown index 166c43e6..c6fee5d7 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -166,6 +166,10 @@ int main() { int i1 = 1, i2 = 2; // Shorthand for multiple declaration float f1 = 1.0, f2 = 2.0; + //more shorthands: + int a, b, c; + a = b = c = 0; + // Arithmetic is straightforward i1 + i2; // => 3 i2 - i1; // => 1 @@ -339,7 +343,7 @@ int main() { printf("%d\n", x); // => Prints 1 // Arrays are a good way to allocate a contiguous block of memory - int x_array[20]; + int x_array[20]; //declares array of size 20 (cannot change size) int xx; for (xx = 0; xx < 20; xx++) { x_array[xx] = 20 - xx; -- cgit v1.2.3 From dfd8afb4969c76b71a852e7bc8378b7e7f8f4bb3 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 16:36:16 -0500 Subject: Add ASCII chars to Types of C file. --- c.html.markdown | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/c.html.markdown b/c.html.markdown index c6fee5d7..96f253b7 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -98,6 +98,10 @@ int main() { unsigned int ux_int; unsigned long long ux_long_long; + // chars inside single quotes '*' are ASCII versions of + '0' //==> 48 on the ASCII table. + 'A' //==> 65 on the ASCII table. + // sizeof(T) gives you the size of a variable with type T in bytes // sizeof(obj) yields the size of the expression (variable, literal, etc.). printf("%zu\n", sizeof(int)); // => 4 (on most machines with 4-byte words) -- cgit v1.2.3 From 79fdd62c6bcb13c550050efe02d6753d198a5a83 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 16:51:35 -0500 Subject: Add function prototype to C. --- c.html.markdown | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/c.html.markdown b/c.html.markdown index 96f253b7..75025b0c 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -422,6 +422,16 @@ int add_two_ints(int x1, int x2) return x1 + x2; // Use return to return a value } +// Must declare a 'funtion prototype' before main() when creating functions +// in file. +int getInt(char c); // function prototype +int main() { + return 0; +} +int getInt(char w) { //parameter name does not need to match function prototype + return 1; +} + /* Functions are pass-by-value, but you can make your own references with pointers so functions can mutate their values. -- cgit v1.2.3 From 41f65bb3415e7002ef171c351376c1c4d5336746 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 17:04:47 -0500 Subject: Clarified function call by value description. --- c.html.markdown | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index 75025b0c..e6e2559e 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -433,8 +433,12 @@ int getInt(char w) { //parameter name does not need to match function prototype } /* -Functions are pass-by-value, but you can make your own references -with pointers so functions can mutate their values. +Functions are call by value. So when a function is called, the arguments passed +to the function are copies of original arguments (except arrays). Anything you +do to your arguments do not change the value of the actual argument where the +function was called. + +You can use pointers if you need to edit the original argument values. Example: in-place string reversal */ -- cgit v1.2.3 From 394ca958b3b61853b1fe8ec1063b3adb03239178 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 18:42:05 -0500 Subject: Add more notes to null character in C --- c.html.markdown | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/c.html.markdown b/c.html.markdown index e6e2559e..90d0d358 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -27,7 +27,8 @@ Multi-line comments look like this. They work in C89 as well. '\f' // new page '\r' // carriage return '\b' // backspace character -'\0' // null character +'\0' // null character. Usually put at end of strings in C lang. + // hello\n\0. \0 used by convention to mark end of string. //print formatting: "%d" // integer -- cgit v1.2.3 From d632203255085171ce79a106a40797d1d5fa54a3 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 18:54:07 -0500 Subject: Add more notes to function prototype in C. --- c.html.markdown | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index 90d0d358..ee60d168 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -425,13 +425,16 @@ int add_two_ints(int x1, int x2) // Must declare a 'funtion prototype' before main() when creating functions // in file. -int getInt(char c); // function prototype +void getInt(char c); // function prototype int main() { return 0; } -int getInt(char w) { //parameter name does not need to match function prototype - return 1; +void getInt(char w) { //parameter name does not need to match function prototype + ; } +//if function takes no parameters, do: int getInt(void); for function prototype +// and for the function declaration: int getInt(void) {} +// this is to keep compatibility with older versions of C. /* Functions are call by value. So when a function is called, the arguments passed -- cgit v1.2.3 From 8caf3768fb4a1f0fa14ca4765e7f168534c7cd8f Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 19:24:15 -0500 Subject: Add extern notes to C. --- c.html.markdown | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/c.html.markdown b/c.html.markdown index ee60d168..2a828ab7 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -99,7 +99,7 @@ int main() { unsigned int ux_int; unsigned long long ux_long_long; - // chars inside single quotes '*' are ASCII versions of + // chars inside single quotes '*' are character constants. '0' //==> 48 on the ASCII table. 'A' //==> 65 on the ASCII table. @@ -472,6 +472,12 @@ while ((c = getchar()) != EOF) { // EOF constant "end of file". char c = getchar(); } +//if referring to external variables outside function, must use extern keyword. +int i = 0; +void testFunc() { + extern int i; //i here is now using external variable i +} + /* char c[] = "This is a test."; str_reverse(c); -- cgit v1.2.3 From 411d9a9813e8c7174f35540198b6dadc8c0b665c Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 19:29:25 -0500 Subject: Add more escape sequences to C. --- c.html.markdown | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/c.html.markdown b/c.html.markdown index 2a828ab7..4764c38e 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -21,14 +21,21 @@ Multi-line comments look like this. They work in C89 as well. */ //Special characters: +'\a' // alert (bell) character '\n' // newline character '\t' // tab character (left justifies text) '\v' // vertical tab -'\f' // new page +'\f' // new page (formfeed) '\r' // carriage return '\b' // backspace character '\0' // null character. Usually put at end of strings in C lang. // hello\n\0. \0 used by convention to mark end of string. +'\\' // backspace +'\?' // question mark +'\'' // single quote +'\"' // double quote +'\xhh' // hexadecimal number. Example: '\xb' = vertical tab character +'\ooo' // octal number. Example: '\013' = vertical tab character //print formatting: "%d" // integer -- cgit v1.2.3 From 2e8e2b5f3552bd9541a4eac6abba94a767dda8e4 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 20:51:11 -0500 Subject: Add enum to C. --- c.html.markdown | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/c.html.markdown b/c.html.markdown index 4764c38e..0ac603a7 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -54,6 +54,10 @@ Multi-line comments look like this. They work in C89 as well. // Constants: use #define keyword, no semicolon at end. #define DAYS_IN_YEAR = 365 +//enumeration constants are also ways to declare constants. +enum days {SUN = 1, MON, TUE, WED, THU, FRI, SAT}; +// MON gets 2 automatically, TUE gets 3, etc. + // Import headers with #include #include #include -- cgit v1.2.3 From ca32d7a5f2edfe9dad2b43fc849b1495c2b5f889 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 21:16:32 -0500 Subject: Add clarity to characters in character set. --- c.html.markdown | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index 0ac603a7..4e7dae5c 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -110,9 +110,9 @@ int main() { unsigned int ux_int; unsigned long long ux_long_long; - // chars inside single quotes '*' are character constants. - '0' //==> 48 on the ASCII table. - 'A' //==> 65 on the ASCII table. + // chars inside single quotes '*' are integers in your character set. + '0' //==> 48 on the ASCII character set. + 'A' //==> 65 on the ASCII character set. // sizeof(T) gives you the size of a variable with type T in bytes // sizeof(obj) yields the size of the expression (variable, literal, etc.). -- cgit v1.2.3 From e9c92321f4442ca4af75f6cce16d435287dad750 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 31 Aug 2013 21:18:59 -0500 Subject: Add include statement to popular C standar libraries. --- c.html.markdown | 1 + 1 file changed, 1 insertion(+) diff --git a/c.html.markdown b/c.html.markdown index 4e7dae5c..6d95f28b 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -62,6 +62,7 @@ enum days {SUN = 1, MON, TUE, WED, THU, FRI, SAT}; #include #include #include +#include // (File names between are headers from the C standard library.) // For your own headers, use double quotes instead of angle brackets: -- cgit v1.2.3 From 642e7c551e0f6292be403ed893a6695130cf350a Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sun, 1 Sep 2013 10:44:55 -0500 Subject: Add note to while loop in C. --- c.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/c.html.markdown b/c.html.markdown index 6d95f28b..f63adc05 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -260,7 +260,7 @@ int main() { // While loops exist int ii = 0; - while (ii < 10) { + while (ii < 10) { //ANY value not zero is true. printf("%d, ", ii++); // ii++ increments ii in-place // after yielding its value ("postincrement"). } // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, " -- cgit v1.2.3 From 977d226d26c056094a33f38da79d1d9395915f52 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sun, 1 Sep 2013 10:59:30 -0500 Subject: Reworded incrementing operators in C. --- c.html.markdown | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index f63adc05..c5ac7708 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -261,8 +261,7 @@ int main() { // While loops exist int ii = 0; while (ii < 10) { //ANY value not zero is true. - printf("%d, ", ii++); // ii++ increments ii in-place - // after yielding its value ("postincrement"). + printf("%d, ", ii++); // ii++ increments ii AFTER using it's current value. } // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, " printf("\n"); @@ -270,8 +269,7 @@ int main() { int kk = 0; do { printf("%d, ", kk); - } while (++kk < 10); // ++kk increments kk in-place, and yields - // the already incremented value ("preincrement") + } while (++kk < 10); // ++kk increments kk BEFORE using it's current value. // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, " printf("\n"); -- cgit v1.2.3 From 2fab4dc971e3c249dc8be7c365309afb8ab9c209 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sun, 1 Sep 2013 11:10:04 -0500 Subject: Add specific examples of increment and decrement operators to C. --- c.html.markdown | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/c.html.markdown b/c.html.markdown index c5ac7708..e6179ba6 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -226,6 +226,17 @@ int main() { 0 || 1; // => 1 (Logical or) 0 || 0; // => 0 + //Increment and decrement operators: + int j = 0; + char s[]; + int w = 0; + j++; //difference between postfix and prefix explained below + ++j; // in string example. + j--; + --j; + s[j++]; //returns value of j to s THEN increments value of j. + s[++j]; //increments value of j THEN returns value of j to s. + // Bitwise operators! ~0x0F; // => 0xF0 (bitwise negation, "1's complement") 0x0F & 0xF0; // => 0x00 (bitwise AND) -- cgit v1.2.3 From 0ab144ff976c7a701acef552cc8e33b38faa7dbc Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sun, 1 Sep 2013 11:51:25 -0500 Subject: Add conditinal expression (?:) to C. --- c.html.markdown | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/c.html.markdown b/c.html.markdown index e6179ba6..ea047ea0 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -226,6 +226,10 @@ int main() { 0 || 1; // => 1 (Logical or) 0 || 0; // => 0 + //Conditional expression ( ?: ) + int a, b, z; + z = (a > b) ? a : b; // z = max(a, b); + //Increment and decrement operators: int j = 0; char s[]; -- cgit v1.2.3 From c4f541dc92ae149947a49a885292d8ad7ead7aa6 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sun, 1 Sep 2013 13:17:26 -0500 Subject: Add order of evaluation table to C. --- c.html.markdown | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/c.html.markdown b/c.html.markdown index ea047ea0..fd0b7964 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -593,6 +593,31 @@ typedef void (*my_fnp_type)(char *); // ... // my_fnp_type f; + +/////////////////////////////////////// +// Order of Evaluation +/////////////////////////////////////// + +//---------------------------------------------------// +// Operators | Associativity // +//---------------------------------------------------// +// () [] -> . | left to right // +// ! ~ ++ -- + = *(type)sizeof | right to left // +// * / % | left to right // +// + - | left to right // +// << >> | left to right // +// < <= > >= | left to right // +// == != | left to right // +// & | left to right // +// ^ | left to right // +// | | left to right // +// && | left to right // +// || | left to right // +// ?: | right to left // +// = += -= *= /= %= &= ^= |= <<= >>= | right to left // +// , | left to right // +//---------------------------------------------------// + ``` ## Further Reading -- cgit v1.2.3 From de5a359faadffadbff1ccb19ad584ffb1c906796 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Thu, 19 Sep 2013 16:48:09 -0500 Subject: Edit wording of while loop in bash. --- bash.html.markdown | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/bash.html.markdown b/bash.html.markdown index 1473e669..2faa4988 100644 --- a/bash.html.markdown +++ b/bash.html.markdown @@ -53,10 +53,10 @@ else echo "And this is not" fi -# And the usual while loop: +# while loop: while [true] do - echo "put loop content here..." + echo "loop body here..." break done -- cgit v1.2.3 From f28d33fb187bc834e6e2956117039f9abe3b6d9b Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Thu, 19 Sep 2013 17:10:53 -0500 Subject: Edit wording on in c changes. --- c.html.markdown | 53 +++++++++++++++++++++++++---------------------------- 1 file changed, 25 insertions(+), 28 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index fd0b7964..89bfbe6d 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -39,7 +39,7 @@ Multi-line comments look like this. They work in C89 as well. //print formatting: "%d" // integer -"%3d" // minimum length of 3 digits for integer (right justifies text) +"%3d" // integer with minimum of length 3 digits (right justifies text) "%s" // string "%f" // float "%ld" // long @@ -51,7 +51,7 @@ Multi-line comments look like this. They work in C89 as well. "%o" // octal "%%" // prints % -// Constants: use #define keyword, no semicolon at end. +// Constants: #define (no semicolon at end) #define DAYS_IN_YEAR = 365 //enumeration constants are also ways to declare constants. @@ -62,7 +62,6 @@ enum days {SUN = 1, MON, TUE, WED, THU, FRI, SAT}; #include #include #include -#include // (File names between are headers from the C standard library.) // For your own headers, use double quotes instead of angle brackets: @@ -111,7 +110,7 @@ int main() { unsigned int ux_int; unsigned long long ux_long_long; - // chars inside single quotes '*' are integers in your character set. + // chars inside single quotes are integers in machine's character set. '0' //==> 48 on the ASCII character set. 'A' //==> 65 on the ASCII character set. @@ -226,20 +225,14 @@ int main() { 0 || 1; // => 1 (Logical or) 0 || 0; // => 0 - //Conditional expression ( ?: ) + //Conditional expression ( ? : ) int a, b, z; - z = (a > b) ? a : b; // z = max(a, b); + z = (a > b) ? a : b; // "if a > b return a, else return b." //Increment and decrement operators: - int j = 0; - char s[]; - int w = 0; - j++; //difference between postfix and prefix explained below - ++j; // in string example. - j--; - --j; s[j++]; //returns value of j to s THEN increments value of j. s[++j]; //increments value of j THEN returns value of j to s. + // same with j-- and --j // Bitwise operators! ~0x0F; // => 0xF0 (bitwise negation, "1's complement") @@ -267,12 +260,6 @@ int main() { printf("I print\n"); } - // Notes: - // Loops MUST always have a body. If no body is needed, do this: - for (i = 0; i <= 5; i++) { - ; // use semicolon to act as the body (null statement) - } - // While loops exist int ii = 0; while (ii < 10) { //ANY value not zero is true. @@ -297,6 +284,12 @@ int main() { printf("\n"); + // *****NOTES*****: + // Loops MUST always have a body. If no body is needed, do: + for (i = 0; i <= 5; i++) { + ; // use semicolon to act as the body (null statement) + } + // branching with multiple choices: switch() switch (some_integral_expression) { case 0: // labels need to be integral *constant* epxressions @@ -448,18 +441,20 @@ int add_two_ints(int x1, int x2) return x1 + x2; // Use return to return a value } -// Must declare a 'funtion prototype' before main() when creating functions -// in file. +// Must declare a 'funtion prototype' when creating functions before main() void getInt(char c); // function prototype -int main() { +int main() { // main function return 0; } void getInt(char w) { //parameter name does not need to match function prototype ; } -//if function takes no parameters, do: int getInt(void); for function prototype -// and for the function declaration: int getInt(void) {} -// this is to keep compatibility with older versions of C. + +//if function takes no parameters, do: +int getInt(void); for function prototype +// and for the function declaration: +int getInt(void) {} +// (this is to keep compatibility with older versions of C). /* Functions are call by value. So when a function is called, the arguments passed @@ -485,11 +480,13 @@ void str_reverse(char *str_in) } } +///////////////////////////////////// // Built in functions: +///////////////////////////////////// // from stdio.h: -int c = getchar(); //reads character from input. If input = hi, only h is read. -// getchar() can be stored into int or char. I am using int because -// char is not large enough to store EOF used below. +// getchar() +int c = getchar(); //reads character from input. +// If input = hi, 'h' is returned then next call, 'i' returned. while ((c = getchar()) != EOF) { // EOF constant "end of file". // Linux: CTRL+D, Windows: CTRL+X // must have () around getchar() as != is run before =. -- cgit v1.2.3 From 2ef41199266fefc868dd28c3e0ac5dc55daf9d8f Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Fri, 20 Sep 2013 21:53:42 -0500 Subject: Fix typo for 'funtion prototype' --- c.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/c.html.markdown b/c.html.markdown index fd0b7964..68ef7f03 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -448,7 +448,7 @@ int add_two_ints(int x1, int x2) return x1 + x2; // Use return to return a value } -// Must declare a 'funtion prototype' before main() when creating functions +// Must declare a 'function prototype' before main() when creating functions // in file. void getInt(char c); // function prototype int main() { -- cgit v1.2.3 From 7c559d57a88143b0cbe7b16dbd071f0e07c83b32 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Fri, 20 Sep 2013 22:05:08 -0500 Subject: Move special characters to end of file --- c.html.markdown | 61 ++++++++++++++++++++++++++++----------------------------- 1 file changed, 30 insertions(+), 31 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index 2a65d82c..9745ed9a 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -20,37 +20,6 @@ memory management and C will take you as far as you need to go. Multi-line comments look like this. They work in C89 as well. */ -//Special characters: -'\a' // alert (bell) character -'\n' // newline character -'\t' // tab character (left justifies text) -'\v' // vertical tab -'\f' // new page (formfeed) -'\r' // carriage return -'\b' // backspace character -'\0' // null character. Usually put at end of strings in C lang. - // hello\n\0. \0 used by convention to mark end of string. -'\\' // backspace -'\?' // question mark -'\'' // single quote -'\"' // double quote -'\xhh' // hexadecimal number. Example: '\xb' = vertical tab character -'\ooo' // octal number. Example: '\013' = vertical tab character - -//print formatting: -"%d" // integer -"%3d" // integer with minimum of length 3 digits (right justifies text) -"%s" // string -"%f" // float -"%ld" // long -"%3.2f" // minimum 3 digits left and 2 digits right decimal float -"%7.4s" // (can do with strings too) -"%c" // char -"%p" // pointer -"%x" // hexidecimal -"%o" // octal -"%%" // prints % - // Constants: #define (no semicolon at end) #define DAYS_IN_YEAR = 365 @@ -590,6 +559,36 @@ typedef void (*my_fnp_type)(char *); // ... // my_fnp_type f; +//Special characters: +'\a' // alert (bell) character +'\n' // newline character +'\t' // tab character (left justifies text) +'\v' // vertical tab +'\f' // new page (formfeed) +'\r' // carriage return +'\b' // backspace character +'\0' // null character. Usually put at end of strings in C lang. + // hello\n\0. \0 used by convention to mark end of string. +'\\' // backspace +'\?' // question mark +'\'' // single quote +'\"' // double quote +'\xhh' // hexadecimal number. Example: '\xb' = vertical tab character +'\ooo' // octal number. Example: '\013' = vertical tab character + +//print formatting: +"%d" // integer +"%3d" // integer with minimum of length 3 digits (right justifies text) +"%s" // string +"%f" // float +"%ld" // long +"%3.2f" // minimum 3 digits left and 2 digits right decimal float +"%7.4s" // (can do with strings too) +"%c" // char +"%p" // pointer +"%x" // hexidecimal +"%o" // octal +"%%" // prints % /////////////////////////////////////// // Order of Evaluation -- cgit v1.2.3 From 35909645f2dbfedc38b566ec9838c2202cd51e3c Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Fri, 20 Sep 2013 22:13:10 -0500 Subject: Edit note on function prototypes. --- c.html.markdown | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index 9745ed9a..df6cd036 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -41,6 +41,10 @@ enum days {SUN = 1, MON, TUE, WED, THU, FRI, SAT}; void function_1(); void function_2(); +// Must declare a 'function prototype' before main() when functions occur after +// your main() function. +int add_two_ints(int x1, int x2); // function prototype + // Your program's entry point is a function called // main with an integer return type. int main() { @@ -410,15 +414,6 @@ int add_two_ints(int x1, int x2) return x1 + x2; // Use return to return a value } -// Must declare a 'function prototype' before main() when creating functions -void getInt(char c); // function prototype -int main() { // main function - return 0; -} -void getInt(char w) { //parameter name does not need to match function prototype - ; -} - //if function takes no parameters, do: int getInt(void); for function prototype // and for the function declaration: -- cgit v1.2.3 From f471616ccb97e5fd32393f1f408394cfebe0d151 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Fri, 20 Sep 2013 22:16:01 -0500 Subject: Remove .orig file created during merge. --- c.html.markdown.orig | 641 --------------------------------------------------- 1 file changed, 641 deletions(-) delete mode 100644 c.html.markdown.orig diff --git a/c.html.markdown.orig b/c.html.markdown.orig deleted file mode 100644 index 47996cb2..00000000 --- a/c.html.markdown.orig +++ /dev/null @@ -1,641 +0,0 @@ ---- -language: c -filename: learnc.c -contributors: - - ["Adam Bard", "http://adambard.com/"] - - ["Árpád Goretity", "http://twitter.com/H2CO3_iOS"] - ---- - -Ah, C. Still **the** language of modern high-performance computing. - -C is the lowest-level language most programmers will ever use, but -it more than makes up for it with raw speed. Just be aware of its manual -memory management and C will take you as far as you need to go. - -```c -// Single-line comments start with // - only available in C99 and later. - -/* -Multi-line comments look like this. They work in C89 as well. -*/ - -//Special characters: -'\a' // alert (bell) character -'\n' // newline character -'\t' // tab character (left justifies text) -'\v' // vertical tab -'\f' // new page (formfeed) -'\r' // carriage return -'\b' // backspace character -'\0' // null character. Usually put at end of strings in C lang. - // hello\n\0. \0 used by convention to mark end of string. -'\\' // backspace -'\?' // question mark -'\'' // single quote -'\"' // double quote -'\xhh' // hexadecimal number. Example: '\xb' = vertical tab character -'\ooo' // octal number. Example: '\013' = vertical tab character - -//print formatting: -"%d" // integer -"%3d" // integer with minimum of length 3 digits (right justifies text) -"%s" // string -"%f" // float -"%ld" // long -"%3.2f" // minimum 3 digits left and 2 digits right decimal float -"%7.4s" // (can do with strings too) -"%c" // char -"%p" // pointer -"%x" // hexidecimal -"%o" // octal -"%%" // prints % - -// Constants: #define (no semicolon at end) -#define DAYS_IN_YEAR = 365 - -//enumeration constants are also ways to declare constants. -enum days {SUN = 1, MON, TUE, WED, THU, FRI, SAT}; -// MON gets 2 automatically, TUE gets 3, etc. - -// Import headers with #include -#include -#include -#include - -// (File names between are headers from the C standard library.) -// For your own headers, use double quotes instead of angle brackets: -#include "my_header.h" - -// Declare function signatures in advance in a .h file, or at the top of -// your .c file. -void function_1(); -void function_2(); - -// Your program's entry point is a function called -// main with an integer return type. -int main() { - // print output using printf, for "print formatted" - // %d is an integer, \n is a newline - printf("%d\n", 0); // => Prints 0 - // All statements must end with a semicolon - - /////////////////////////////////////// - // Types - /////////////////////////////////////// - - // ints are usually 4 bytes - int x_int = 0; - - // shorts are usually 2 bytes - short x_short = 0; - - // chars are guaranteed to be 1 byte - char x_char = 0; - char y_char = 'y'; // Char literals are quoted with '' - - // longs are often 4 to 8 bytes; long longs are guaranteed to be at least - // 64 bits - long x_long = 0; - long long x_long_long = 0; - - // floats are usually 32-bit floating point numbers - float x_float = 0.0; - - // doubles are usually 64-bit floating-point numbers - double x_double = 0.0; - - // Integral types may be unsigned. - unsigned short ux_short; - unsigned int ux_int; - unsigned long long ux_long_long; - - // chars inside single quotes are integers in machine's character set. - '0' //==> 48 on the ASCII character set. - 'A' //==> 65 on the ASCII character set. - - // sizeof(T) gives you the size of a variable with type T in bytes - // sizeof(obj) yields the size of the expression (variable, literal, etc.). - printf("%zu\n", sizeof(int)); // => 4 (on most machines with 4-byte words) - - - // If the argument of the `sizeof` operator an expression, then its argument - // is not evaluated (except VLAs (see below)). - // The value it yields in this case is a compile-time constant. - int a = 1; - size_t size = sizeof(a++); // a++ is not evaluated - printf("sizeof(a++) = %zu where a = %d\n", size, a); - // prints "sizeof(a++) = 4 where a = 1" (on a 32-bit architecture) - - // Arrays must be initialized with a concrete size. - char my_char_array[20]; // This array occupies 1 * 20 = 20 bytes - int my_int_array[20]; // This array occupies 4 * 20 = 80 bytes - // (assuming 4-byte words) - - - // You can initialize an array to 0 thusly: - char my_array[20] = {0}; - - // Indexing an array is like other languages -- or, - // rather, other languages are like C - my_array[0]; // => 0 - - // Arrays are mutable; it's just memory! - my_array[1] = 2; - printf("%d\n", my_array[1]); // => 2 - - // In C99 (and as an optional feature in C11), variable-length arrays (VLAs) - // can be declared as well. The size of such an array need not be a compile - // time constant: - printf("Enter the array size: "); // ask the user for an array size - char buf[0x100]; - fgets(buf, sizeof buf, stdin); - - // strtoul parses a string to an unsigned integer - size_t size = strtoul(buf, NULL, 10); - int var_length_array[size]; // declare the VLA - printf("sizeof array = %zu\n", sizeof var_length_array); - - // A possible outcome of this program may be: - // > Enter the array size: 10 - // > sizeof array = 40 - - // Strings are just arrays of chars terminated by a NUL (0x00) byte, - // represented in strings as the special character '\0'. - // (We don't have to include the NUL byte in string literals; the compiler - // inserts it at the end of the array for us.) - char a_string[20] = "This is a string"; - printf("%s\n", a_string); // %s formats a string - - printf("%d\n", a_string[16]); // => 0 - // i.e., byte #17 is 0 (as are 18, 19, and 20) - - // If we have characters between single quotes, that's a character literal. - // It's of type `int`, and *not* `char` (for historical reasons). - int cha = 'a'; // fine - char chb = 'a'; // fine too (implicit conversion from int to char) - - /////////////////////////////////////// - // Operators - /////////////////////////////////////// - - int i1 = 1, i2 = 2; // Shorthand for multiple declaration - float f1 = 1.0, f2 = 2.0; - - //more shorthands: - int a, b, c; - a = b = c = 0; - - // Arithmetic is straightforward - i1 + i2; // => 3 - i2 - i1; // => 1 - i2 * i1; // => 2 - i1 / i2; // => 0 (0.5, but truncated towards 0) - - f1 / f2; // => 0.5, plus or minus epsilon - // Floating-point numbers and calculations are not exact - - // Modulo is there as well - 11 % 3; // => 2 - - // Comparison operators are probably familiar, but - // there is no boolean type in c. We use ints instead. - // (Or _Bool or bool in C99.) - // 0 is false, anything else is true. (The comparison - // operators always yield 0 or 1.) - 3 == 2; // => 0 (false) - 3 != 2; // => 1 (true) - 3 > 2; // => 1 - 3 < 2; // => 0 - 2 <= 2; // => 1 - 2 >= 2; // => 1 - - // C is not Python - comparisons don't chain. - int a = 1; - // WRONG: - int between_0_and_2 = 0 < a < 2; - // Correct: - int between_0_and_2 = 0 < a && a < 2; - - // Logic works on ints - !3; // => 0 (Logical not) - !0; // => 1 - 1 && 1; // => 1 (Logical and) - 0 && 1; // => 0 - 0 || 1; // => 1 (Logical or) - 0 || 0; // => 0 - - //Conditional expression ( ? : ) - int a, b, z; - z = (a > b) ? a : b; // "if a > b return a, else return b." - - //Increment and decrement operators: - s[j++]; //returns value of j to s THEN increments value of j. - s[++j]; //increments value of j THEN returns value of j to s. - // same with j-- and --j - - // Bitwise operators! - ~0x0F; // => 0xF0 (bitwise negation, "1's complement") - 0x0F & 0xF0; // => 0x00 (bitwise AND) - 0x0F | 0xF0; // => 0xFF (bitwise OR) - 0x04 ^ 0x0F; // => 0x0B (bitwise XOR) - 0x01 << 1; // => 0x02 (bitwise left shift (by 1)) - 0x02 >> 1; // => 0x01 (bitwise right shift (by 1)) - - // Be careful when shifting signed integers - the following are undefined: - // - shifting into the sign bit of a signed integer (int a = 1 << 32) - // - left-shifting a negative number (int a = -1 << 2) - // - shifting by an offset which is >= the width of the type of the LHS: - // int a = 1 << 32; // UB if int is 32 bits wide - - /////////////////////////////////////// - // Control Structures - /////////////////////////////////////// - - if (0) { - printf("I am never run\n"); - } else if (0) { - printf("I am also never run\n"); - } else { - printf("I print\n"); - } - - // While loops exist - int ii = 0; - while (ii < 10) { //ANY value not zero is true. - printf("%d, ", ii++); // ii++ increments ii AFTER using it's current value. - } // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, " - - printf("\n"); - - int kk = 0; - do { - printf("%d, ", kk); - } while (++kk < 10); // ++kk increments kk BEFORE using it's current value. - // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, " - - printf("\n"); - - // For loops too - int jj; - for (jj=0; jj < 10; jj++) { - printf("%d, ", jj); - } // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, " - - printf("\n"); - - // *****NOTES*****: - // Loops MUST always have a body. If no body is needed, do: - for (i = 0; i <= 5; i++) { - ; // use semicolon to act as the body (null statement) - } - - // branching with multiple choices: switch() - switch (some_integral_expression) { - case 0: // labels need to be integral *constant* epxressions - do_stuff(); - break; // if you don't break, control flow falls over labels - case 1: - do_something_else(); - break; - default: - // if `some_integral_expression` didn't match any of the labels - fputs("error!\n", stderr); - exit(-1); - break; - } - - - /////////////////////////////////////// - // Typecasting - /////////////////////////////////////// - - // Every value in C has a type, but you can cast one value into another type - // if you want (with some constraints). - - int x_hex = 0x01; // You can assign vars with hex literals - - // Casting between types will attempt to preserve their numeric values - printf("%d\n", x_hex); // => Prints 1 - printf("%d\n", (short) x_hex); // => Prints 1 - printf("%d\n", (char) x_hex); // => Prints 1 - - // Types will overflow without warning - printf("%d\n", (unsigned char) 257); // => 1 (Max char = 255 if char is 8 bits long) - - // For determining the max value of a `char`, a `signed char` and an `unisigned char`, - // respectively, use the CHAR_MAX, SCHAR_MAX and UCHAR_MAX macros from - - // Integral types can be cast to floating-point types, and vice-versa. - printf("%f\n", (float)100); // %f formats a float - printf("%lf\n", (double)100); // %lf formats a double - printf("%d\n", (char)100.0); - - /////////////////////////////////////// - // Pointers - /////////////////////////////////////// - - // A pointer is a variable declared to store a memory address. Its declaration will - // also tell you the type of data it points to. You can retrieve the memory address - // of your variables, then mess with them. - - int x = 0; - printf("%p\n", (void *)&x); // Use & to retrieve the address of a variable - // (%p formats an object pointer of type void *) - // => Prints some address in memory; - - - // Pointers start with * in their declaration - int *px, not_a_pointer; // px is a pointer to an int - px = &x; // Stores the address of x in px - printf("%p\n", (void *)px); // => Prints some address in memory - printf("%zu, %zu\n", sizeof(px), sizeof(not_a_pointer)); - // => Prints "8, 4" on a typical 64-bit system - - // To retreive the value at the address a pointer is pointing to, - // put * in front to de-reference it. - // Note: yes, it may be confusing that '*' is used for _both_ declaring a - // pointer and dereferencing it. - printf("%d\n", *px); // => Prints 0, the value of x - - // You can also change the value the pointer is pointing to. - // We'll have to wrap the de-reference in parenthesis because - // ++ has a higher precedence than *. - (*px)++; // Increment the value px is pointing to by 1 - printf("%d\n", *px); // => Prints 1 - printf("%d\n", x); // => Prints 1 - - // Arrays are a good way to allocate a contiguous block of memory - int x_array[20]; //declares array of size 20 (cannot change size) - int xx; - for (xx = 0; xx < 20; xx++) { - x_array[xx] = 20 - xx; - } // Initialize x_array to 20, 19, 18,... 2, 1 - - // Declare a pointer of type int and initialize it to point to x_array - int* x_ptr = x_array; - // x_ptr now points to the first element in the array (the integer 20). - // This works because arrays often decay into pointers to their first element. - // For example, when an array is passed to a function or is assigned to a pointer, - // it decays into (implicitly converted to) a pointer. - // Exceptions: when the array is the argument of the `&` (address-od) operator: - int arr[10]; - int (*ptr_to_arr)[10] = &arr; // &arr is NOT of type `int *`! - // It's of type "pointer to array" (of ten `int`s). - // or when the array is a string literal used for initializing a char array: - char arr[] = "foobarbazquirk"; - // or when it's the argument of the `sizeof` or `alignof` operator: - int arr[10]; - int *ptr = arr; // equivalent with int *ptr = &arr[0]; - printf("%zu %zu\n", sizeof arr, sizeof ptr); // probably prints "40, 4" or "40, 8" - - - // Pointers are incremented and decremented based on their type - // (this is called pointer arithmetic) - printf("%d\n", *(x_ptr + 1)); // => Prints 19 - printf("%d\n", x_array[1]); // => Prints 19 - - // You can also dynamically allocate contiguous blocks of memory with the - // standard library function malloc, which takes one argument of type size_t - // representing the number of bytes to allocate (usually from the heap, although this - // may not be true on e. g. embedded systems - the C standard says nothing about it). - int *my_ptr = malloc(sizeof(*my_ptr) * 20); - for (xx = 0; xx < 20; xx++) { - *(my_ptr + xx) = 20 - xx; // my_ptr[xx] = 20-xx - } // Initialize memory to 20, 19, 18, 17... 2, 1 (as ints) - - // Dereferencing memory that you haven't allocated gives - // "unpredictable results" - the program is said to invoke "undefined behavior" - printf("%d\n", *(my_ptr + 21)); // => Prints who-knows-what? It may even crash. - - // When you're done with a malloc'd block of memory, you need to free it, - // or else no one else can use it until your program terminates - // (this is called a "memory leak"): - free(my_ptr); - - // Strings are arrays of char, but they are usually represented as a - // pointer-to-char (which is a pointer to the first element of the array). - // It's good practice to use `const char *' when referring to a string literal, - // since string literals shall not be modified (i. e. "foo"[0] = 'a' is ILLEGAL.) - const char *my_str = "This is my very own string literal"; - printf("%c\n", *my_str); // => 'T' - - // This is not the case if the string is an array - // (potentially initialized with a string literal) - // that resides in writable memory, as in: - char foo[] = "foo"; - foo[0] = 'a'; // this is legal, foo now contains "aoo" - - function_1(); -} // end main function - -/////////////////////////////////////// -// Functions -/////////////////////////////////////// - -// Function declaration syntax: -// () - -int add_two_ints(int x1, int x2) -{ - return x1 + x2; // Use return to return a value -} - -<<<<<<< HEAD -// Must declare a 'function prototype' before main() when creating functions -// in file. -======= -// Must declare a 'funtion prototype' when creating functions before main() ->>>>>>> f28d33fb187bc834e6e2956117039f9abe3b6d9b -void getInt(char c); // function prototype -int main() { // main function - return 0; -} -void getInt(char w) { //parameter name does not need to match function prototype - ; -} - -//if function takes no parameters, do: -int getInt(void); for function prototype -// and for the function declaration: -int getInt(void) {} -// (this is to keep compatibility with older versions of C). - -/* -Functions are call by value. So when a function is called, the arguments passed -to the function are copies of original arguments (except arrays). Anything you -do to your arguments do not change the value of the actual argument where the -function was called. - -You can use pointers if you need to edit the original argument values. - -Example: in-place string reversal -*/ - -// A void function returns no value -void str_reverse(char *str_in) -{ - char tmp; - int ii = 0; - size_t len = strlen(str_in); // `strlen()` is part of the c standard library - for (ii = 0; ii < len / 2; ii++) { - tmp = str_in[ii]; - str_in[ii] = str_in[len - ii - 1]; // ii-th char from end - str_in[len - ii - 1] = tmp; - } -} - -///////////////////////////////////// -// Built in functions: -///////////////////////////////////// -// from stdio.h: -// getchar() -int c = getchar(); //reads character from input. -// If input = hi, 'h' is returned then next call, 'i' returned. -while ((c = getchar()) != EOF) { // EOF constant "end of file". - // Linux: CTRL+D, Windows: CTRL+X - // must have () around getchar() as != is run before =. - putchar(c); //prints character (without newline at end) - char c = getchar(); -} - -//if referring to external variables outside function, must use extern keyword. -int i = 0; -void testFunc() { - extern int i; //i here is now using external variable i -} - -/* -char c[] = "This is a test."; -str_reverse(c); -printf("%s\n", c); // => ".tset a si sihT" -*/ - -/////////////////////////////////////// -// User-defined types and structs -/////////////////////////////////////// - -// Typedefs can be used to create type aliases -typedef int my_type; -my_type my_type_var = 0; - -// Structs are just collections of data, the members are allocated sequentially, -// in the order they are written: -struct rectangle { - int width; - int height; -}; - -// It's not generally true that -// sizeof(struct rectangle) == sizeof(int) + sizeof(int) -// due to potential padding between the structure members (this is for alignment -// reasons). [1] - -void function_1() -{ - struct rectangle my_rec; - - // Access struct members with . - my_rec.width = 10; - my_rec.height = 20; - - // You can declare pointers to structs - struct rectangle *my_rec_ptr = &my_rec; - - // Use dereferencing to set struct pointer members... - (*my_rec_ptr).width = 30; - - // ... or even better: prefer the -> shorthand for the sake of readability - my_rec_ptr->height = 10; // Same as (*my_rec_ptr).height = 10; -} - -// You can apply a typedef to a struct for convenience -typedef struct rectangle rect; - -int area(rect r) -{ - return r.width * r.height; -} - -// if you have large structs, you can pass them "by pointer" to avoid copying -// the whole struct: -int area(const rect *r) -{ - return r->width * r->height; -} - -/////////////////////////////////////// -// Function pointers -/////////////////////////////////////// -/* -At runtime, functions are located at known memory addresses. Function pointers are -much like any other pointer (they just store a memory address), but can be used -to invoke functions directly, and to pass handlers (or callback functions) around. -However, definition syntax may be initially confusing. - -Example: use str_reverse from a pointer -*/ -void str_reverse_through_pointer(char *str_in) { - // Define a function pointer variable, named f. - void (*f)(char *); // Signature should exactly match the target function. - f = &str_reverse; // Assign the address for the actual function (determined at runtime) - // f = str_reverse; would work as well - functions decay into pointers, similar to arrays - (*f)(str_in); // Just calling the function through the pointer - // f(str_in); // That's an alternative but equally valid syntax for calling it. -} - -/* -As long as function signatures match, you can assign any function to the same pointer. -Function pointers are usually typedef'd for simplicity and readability, as follows: -*/ - -typedef void (*my_fnp_type)(char *); - -// Then used when declaring the actual pointer variable: -// ... -// my_fnp_type f; - - -/////////////////////////////////////// -// Order of Evaluation -/////////////////////////////////////// - -//---------------------------------------------------// -// Operators | Associativity // -//---------------------------------------------------// -// () [] -> . | left to right // -// ! ~ ++ -- + = *(type)sizeof | right to left // -// * / % | left to right // -// + - | left to right // -// << >> | left to right // -// < <= > >= | left to right // -// == != | left to right // -// & | left to right // -// ^ | left to right // -// | | left to right // -// && | left to right // -// || | left to right // -// ?: | right to left // -// = += -= *= /= %= &= ^= |= <<= >>= | right to left // -// , | left to right // -//---------------------------------------------------// - -``` - -## Further Reading - -Best to find yourself a copy of [K&R, aka "The C Programming Language"](https://en.wikipedia.org/wiki/The_C_Programming_Language) -It is *the* book about C, written by the creators of C. Be careful, though - it's ancient and it contains some -inaccuracies (well, ideas that are not considered good anymore) or now-changed practices. - -Another good resource is [Learn C the hard way](http://c.learncodethehardway.org/book/). - -If you have a question, read the [compl.lang.c Frequently Asked Questions](http://c-faq.com). - -It's very important to use proper spacing, indentation and to be consistent with your coding style in general. -Readable code is better than clever code and fast code. For a good, sane coding style to adopt, see the -[Linux kernel coding stlye](https://www.kernel.org/doc/Documentation/CodingStyle). - -Other than that, Google is your friend. - -[1] http://stackoverflow.com/questions/119123/why-isnt-sizeof-for-a-struct-equal-to-the-sum-of-sizeof-of-each-member -- cgit v1.2.3 From ec7ee88698bf32bfe6e931865e94d2dac8f41c80 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Fri, 20 Sep 2013 22:19:07 -0500 Subject: Add to ? : example in C. --- c.html.markdown | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index df6cd036..f1e328cf 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -199,8 +199,10 @@ int main() { 0 || 0; // => 0 //Conditional expression ( ? : ) - int a, b, z; - z = (a > b) ? a : b; // "if a > b return a, else return b." + int a = 5; + int b = 10; + int z; + z = (a > b) ? a : b; // => 10 "if a > b return a, else return b." //Increment and decrement operators: s[j++]; //returns value of j to s THEN increments value of j. -- cgit v1.2.3 From 868be425a6602020f275404a8776d48f3d6d2715 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Fri, 20 Sep 2013 22:31:04 -0500 Subject: Add to notes on increment and decrement operators. --- c.html.markdown | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index f1e328cf..f67f6c4a 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -205,8 +205,11 @@ int main() { z = (a > b) ? a : b; // => 10 "if a > b return a, else return b." //Increment and decrement operators: - s[j++]; //returns value of j to s THEN increments value of j. - s[++j]; //increments value of j THEN returns value of j to s. + char *s = "iLoveC" + int j = 0; + s[j++]; // => "i" Returns value of j to s THEN increments value of j. + j = 0; + s[++j]; // => "L" Increments value of j THEN returns value of j to s. // same with j-- and --j // Bitwise operators! -- cgit v1.2.3 From 67cd987efa06141e5dac74f07fa8f561265c835a Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Fri, 20 Sep 2013 22:33:19 -0500 Subject: Declare variable before empty for loop. --- c.html.markdown | 1 + 1 file changed, 1 insertion(+) diff --git a/c.html.markdown b/c.html.markdown index f67f6c4a..d075ea0e 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -264,6 +264,7 @@ int main() { // *****NOTES*****: // Loops MUST always have a body. If no body is needed, do: + int i; for (i = 0; i <= 5; i++) { ; // use semicolon to act as the body (null statement) } -- cgit v1.2.3 From 981cc871a4d4e5473e580dee8574a119ac8a9723 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Fri, 20 Sep 2013 22:37:40 -0500 Subject: Edit getchar() notes. --- c.html.markdown | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index d075ea0e..ee35cdd2 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -453,15 +453,14 @@ void str_reverse(char *str_in) ///////////////////////////////////// // Built in functions: ///////////////////////////////////// -// from stdio.h: -// getchar() -int c = getchar(); //reads character from input. +// from: #include +// ** getchar() ** +// int c = getchar(); //reads character from input. // If input = hi, 'h' is returned then next call, 'i' returned. while ((c = getchar()) != EOF) { // EOF constant "end of file". // Linux: CTRL+D, Windows: CTRL+X // must have () around getchar() as != is run before =. putchar(c); //prints character (without newline at end) - char c = getchar(); } //if referring to external variables outside function, must use extern keyword. -- cgit v1.2.3 From 38de481179484d597d44fa934f87a5f21ebfaa6c Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sat, 23 Nov 2013 22:40:52 -0600 Subject: Add variety to function prototypes. --- c.html.markdown | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index ee35cdd2..b4a874d3 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -38,8 +38,8 @@ enum days {SUN = 1, MON, TUE, WED, THU, FRI, SAT}; // Declare function signatures in advance in a .h file, or at the top of // your .c file. -void function_1(); -void function_2(); +void function_1(char s[]); +int function_2(void); // Must declare a 'function prototype' before main() when functions occur after // your main() function. -- cgit v1.2.3 From e63232d2de1e2058dd381fe1094c7f775f2e3eb8 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sun, 24 Nov 2013 14:17:32 -0600 Subject: Add static description to C. --- c.html.markdown | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/c.html.markdown b/c.html.markdown index b4a874d3..7b95c969 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -469,6 +469,13 @@ void testFunc() { extern int i; //i here is now using external variable i } +//if external variable should only be visible to functions in the source file +// they are declared in, use static: +static int i = 0; //other source files using testFunc() cannot access variable i +void testFunc() { + extern int i; +} + /* char c[] = "This is a test."; str_reverse(c); -- cgit v1.2.3 From af9cc6e9b9748e43cb1c02013fe92465c3455503 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sun, 24 Nov 2013 14:25:30 -0600 Subject: Edit static description wording. Add note about private functions. --- c.html.markdown | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index 7b95c969..ab09a4a2 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -469,12 +469,12 @@ void testFunc() { extern int i; //i here is now using external variable i } -//if external variable should only be visible to functions in the source file -// they are declared in, use static: -static int i = 0; //other source files using testFunc() cannot access variable i +//make external variables private to source file with static: +static int i = 0; //other files using testFunc() cannot access variable i void testFunc() { extern int i; } +//**You may also declare functions as static to make them private** /* char c[] = "This is a test."; -- cgit v1.2.3 From bb4f644a19a086c3c6b32891a7240cc140b379f4 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sun, 24 Nov 2013 15:01:24 -0600 Subject: Fix #define as it does not use = sign. --- c.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/c.html.markdown b/c.html.markdown index ab09a4a2..d8eccd78 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -21,7 +21,7 @@ Multi-line comments look like this. They work in C89 as well. */ // Constants: #define (no semicolon at end) -#define DAYS_IN_YEAR = 365 +#define DAYS_IN_YEAR 365 //enumeration constants are also ways to declare constants. enum days {SUN = 1, MON, TUE, WED, THU, FRI, SAT}; -- cgit v1.2.3 From 5c7f6d70b9477fcd4fe64460704d7dcf48799f98 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sun, 24 Nov 2013 16:58:21 -0600 Subject: Remove bad description of function prototypes. --- c.html.markdown | 6 ------ 1 file changed, 6 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index d8eccd78..d029a00f 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -420,12 +420,6 @@ int add_two_ints(int x1, int x2) return x1 + x2; // Use return to return a value } -//if function takes no parameters, do: -int getInt(void); for function prototype -// and for the function declaration: -int getInt(void) {} -// (this is to keep compatibility with older versions of C). - /* Functions are call by value. So when a function is called, the arguments passed to the function are copies of original arguments (except arrays). Anything you -- cgit v1.2.3 From 67a5236629b6c7748b609f23c0362925b5c4774d Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Sun, 24 Nov 2013 23:26:11 -0600 Subject: Add multi-dimensional array description. --- c.html.markdown | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/c.html.markdown b/c.html.markdown index d029a00f..f4edfca5 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -148,6 +148,14 @@ int main() { int cha = 'a'; // fine char chb = 'a'; // fine too (implicit conversion from int to char) + //Multi-dimensional arrays: + int multi_array[2][5] = { + {1, 2, 3, 4, 5}, + {6, 7, 8, 9, 0} + } + //access elements: + int array_int = multi_array[0][2]; //=> 3 + /////////////////////////////////////// // Operators /////////////////////////////////////// -- cgit v1.2.3 From df3cc00f5233dac96c0e063d87d3552f493e25f6 Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Mon, 25 Nov 2013 09:21:40 -0600 Subject: Remove bad examples, reword places. --- c.html.markdown | 43 +++++++++++++++---------------------------- 1 file changed, 15 insertions(+), 28 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index f4edfca5..4187d757 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -20,7 +20,7 @@ memory management and C will take you as far as you need to go. Multi-line comments look like this. They work in C89 as well. */ -// Constants: #define (no semicolon at end) +// Constants: #define #define DAYS_IN_YEAR 365 //enumeration constants are also ways to declare constants. @@ -38,7 +38,7 @@ enum days {SUN = 1, MON, TUE, WED, THU, FRI, SAT}; // Declare function signatures in advance in a .h file, or at the top of // your .c file. -void function_1(char s[]); +void function_1(char c); int function_2(void); // Must declare a 'function prototype' before main() when functions occur after @@ -84,8 +84,8 @@ int main() { unsigned long long ux_long_long; // chars inside single quotes are integers in machine's character set. - '0' //==> 48 on the ASCII character set. - 'A' //==> 65 on the ASCII character set. + '0' // => 48 in the ASCII character set. + 'A' // => 65 in the ASCII character set. // sizeof(T) gives you the size of a variable with type T in bytes // sizeof(obj) yields the size of the expression (variable, literal, etc.). @@ -154,16 +154,16 @@ int main() { {6, 7, 8, 9, 0} } //access elements: - int array_int = multi_array[0][2]; //=> 3 + int array_int = multi_array[0][2]; // => 3 /////////////////////////////////////// // Operators /////////////////////////////////////// - int i1 = 1, i2 = 2; // Shorthand for multiple declaration + // Shorthands for multiple declarations: + int i1 = 1, i2 = 2; float f1 = 1.0, f2 = 2.0; - //more shorthands: int a, b, c; a = b = c = 0; @@ -215,9 +215,9 @@ int main() { //Increment and decrement operators: char *s = "iLoveC" int j = 0; - s[j++]; // => "i" Returns value of j to s THEN increments value of j. + s[j++]; // => "i". Returns the j-th item of s THEN increments value of j. j = 0; - s[++j]; // => "L" Increments value of j THEN returns value of j to s. + s[++j]; // => "L". Increments value of j THEN returns j-th value of s. // same with j-- and --j // Bitwise operators! @@ -271,7 +271,7 @@ int main() { printf("\n"); // *****NOTES*****: - // Loops MUST always have a body. If no body is needed, do: + // Loops and Functions MUST have a body. If no body is needed: int i; for (i = 0; i <= 5; i++) { ; // use semicolon to act as the body (null statement) @@ -429,12 +429,12 @@ int add_two_ints(int x1, int x2) } /* -Functions are call by value. So when a function is called, the arguments passed -to the function are copies of original arguments (except arrays). Anything you -do to your arguments do not change the value of the actual argument where the -function was called. +Functions are call by value. When a function is called, the arguments passed to +the function are copies of the original arguments (except arrays). Anything you +do to the arguments in the function do not change the value of the original +argument where the function was called. -You can use pointers if you need to edit the original argument values. +Use pointers if you need to edit the original argument values. Example: in-place string reversal */ @@ -452,19 +452,6 @@ void str_reverse(char *str_in) } } -///////////////////////////////////// -// Built in functions: -///////////////////////////////////// -// from: #include -// ** getchar() ** -// int c = getchar(); //reads character from input. -// If input = hi, 'h' is returned then next call, 'i' returned. -while ((c = getchar()) != EOF) { // EOF constant "end of file". - // Linux: CTRL+D, Windows: CTRL+X - // must have () around getchar() as != is run before =. - putchar(c); //prints character (without newline at end) -} - //if referring to external variables outside function, must use extern keyword. int i = 0; void testFunc() { -- cgit v1.2.3