diff options
| -rw-r--r-- | c.html.markdown | 67 |
1 files changed, 33 insertions, 34 deletions
diff --git a/c.html.markdown b/c.html.markdown index b0c77e16..8e170300 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -23,9 +23,9 @@ Multi-line comments look like this. They work in C89 as well. // Constants: #define <keyword> #define DAYS_IN_YEAR 365 - // Enumeration constants are also ways to declare constants. + // 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. +// MON gets 2 automatically, TUE gets 3, etc. // Import headers with #include #include <stdlib.h> @@ -43,7 +43,7 @@ int function_2(void); // Must declare a 'function prototype' before main() when functions occur after // your main() function. -int add_two_ints(int x1, int x2); // function prototype +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. @@ -57,7 +57,7 @@ int main() { // Types /////////////////////////////////////// - // ints are usually 4 bytes + // ints are usually 4 bytes int x_int = 0; // shorts are usually 2 bytes @@ -70,7 +70,7 @@ int main() { // 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; + long long x_long_long = 0; // floats are usually 32-bit floating point numbers float x_float = 0.0; @@ -83,9 +83,9 @@ int main() { unsigned int ux_int; unsigned long long ux_long_long; - // chars inside single quotes are integers in machine's character set. - '0'; // => 48 in the ASCII character set. - 'A'; // => 65 in the ASCII character set. + // chars inside single quotes are integers in machine's 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.). @@ -96,7 +96,7 @@ int main() { // is not evaluated (except VLAs (see below)). // The value it yields in this case is a compile-time constant. int a = 1; - // size_t is an unsigned integer type of at least 2 bytes used to represent + // size_t is an unsigned integer type of at least 2 bytes used to represent // the size of an object. size_t size = sizeof(a++); // a++ is not evaluated printf("sizeof(a++) = %zu where a = %d\n", size, a); @@ -163,7 +163,7 @@ int main() { /////////////////////////////////////// // Shorthands for multiple declarations: - int i1 = 1, i2 = 2; + int i1 = 1, i2 = 2; float f1 = 1.0, f2 = 2.0; int b, c; @@ -184,7 +184,7 @@ int main() { // 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 + // 0 is false, anything else is true. (The comparison // operators always yield 0 or 1.) 3 == 2; // => 0 (false) 3 != 2; // => 1 (true) @@ -211,14 +211,14 @@ int main() { int e = 5; int f = 10; int z; - z = (a > b) ? a : b; // => 10 "if a > b return a, else return b." + z = (a > b) ? a : b; // => 10 "if a > b return a, else return b." //Increment and decrement operators: char *s = "iLoveC"; int j = 0; 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 j-th value of s. + j = 0; + s[++j]; // => "L". Increments value of j THEN returns j-th value of s. // same with j-- and --j // Bitwise operators! @@ -249,7 +249,7 @@ int main() { // While loops exist int ii = 0; - while (ii < 10) { //ANY value not zero is true. + while (ii < 10) { //ANY value not zero is true. printf("%d, ", ii++); // ii++ increments ii AFTER using its current value. } // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, " @@ -281,10 +281,10 @@ int main() { // branching with multiple choices: switch() switch (a) { case 0: // labels need to be integral *constant* expressions - //do_stuff(); + printf("Hey, 'a' equals 0!\n"); break; // if you don't break, control flow falls over labels case 1: - //do_something_else(); + printf("Huh, 'a' equals 1!\n"); break; default: // if `some_integral_expression` didn't match any of the labels @@ -292,7 +292,6 @@ int main() { exit(-1); break; } - /////////////////////////////////////// // Typecasting @@ -324,7 +323,7 @@ int main() { /////////////////////////////////////// // 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 + // 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; @@ -362,7 +361,7 @@ int main() { // 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). + // 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. @@ -396,7 +395,7 @@ int main() { // "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, + // 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); @@ -430,12 +429,12 @@ int add_two_ints(int x1, int x2) } /* -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. +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. -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 */ @@ -528,18 +527,18 @@ int areaptr(const rect *r) } /////////////////////////////////////// -// Function pointers +// Function pointers /////////////////////////////////////// /* At run time, 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 +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. + // 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 run time) // f = str_reverse; would work as well - functions decay into pointers, similar to arrays @@ -556,7 +555,7 @@ typedef void (*my_fnp_type)(char *); // Then used when declaring the actual pointer variable: // ... -// my_fnp_type f; +// my_fnp_type f; //Special characters: /* @@ -567,8 +566,8 @@ typedef void (*my_fnp_type)(char *); '\f'; // new page (form feed) '\r'; // carriage return '\b'; // backspace character -'\0'; // NULL character. Usually put at end of strings in C. -// hello\n\0. \0 used by convention to mark end of string. +'\0'; // NULL character. Usually put at end of strings in C. +// hello\n\0. \0 used by convention to mark end of string. '\\'; // backslash '\?'; // question mark '\''; // single quote @@ -582,13 +581,13 @@ typedef void (*my_fnp_type)(char *); "%s"; // string "%f"; // float "%ld"; // long -"%3.2f"; // minimum 3 digits left and 2 digits right decimal float +"%3.2f"; // minimum 3 digits left and 2 digits right decimal float "%7.4s"; // (can do with strings too) "%c"; // char "%p"; // pointer "%x"; // hexadecimal "%o"; // octal -"%%"; // prints % +"%%"; // prints % */ /////////////////////////////////////// // Order of Evaluation |