diff options
Diffstat (limited to 'c.html.markdown')
| -rw-r--r-- | c.html.markdown | 53 |
1 files changed, 23 insertions, 30 deletions
diff --git a/c.html.markdown b/c.html.markdown index d92d2ee6..18503eab 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -36,7 +36,6 @@ Multi-line comments don't nest /* Be careful */ // comment ends on this line... enum days {SUN = 1, MON, TUE, WED, THU, FRI, SAT}; // MON gets 2 automatically, TUE gets 3, etc. - // Import headers with #include #include <stdlib.h> #include <stdio.h> @@ -114,7 +113,6 @@ int main (int argc, char** argv) // 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 is an expression, then its argument // is not evaluated (except VLAs (see below)). // The value it yields in this case is a compile-time constant. @@ -130,7 +128,6 @@ int main (int argc, char** argv) 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}; @@ -146,9 +143,9 @@ int main (int argc, char** argv) // 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 - int size; - fscanf(stdin, "%d", &size); - int var_length_array[size]; // declare the VLA + int array_size; + fscanf(stdin, "%d", &array_size); + int var_length_array[array_size]; // declare the VLA printf("sizeof array = %zu\n", sizeof var_length_array); // Example: @@ -205,7 +202,7 @@ int main (int argc, char** argv) 11 % 3; // => 2 // Comparison operators are probably familiar, but - // there is no Boolean type in c. We use ints instead. + // 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.) @@ -239,11 +236,9 @@ int main (int argc, char** argv) z = (e > f) ? e : f; // => 10 "if e > f return e, else return f." // 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. + int s = j++; // Return j THEN increase j. (s = 0, j = 1) + s = ++j; // Increase j THEN return j. (s = 2, j = 2) // same with j-- and --j // Bitwise operators! @@ -274,7 +269,7 @@ int main (int argc, char** argv) // While loops exist int ii = 0; - while (ii < 10) { //ANY value not zero is true. + while (ii < 10) { //ANY value less than ten is true. printf("%d, ", ii++); // ii++ increments ii AFTER using its current value. } // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, " @@ -347,7 +342,6 @@ int main (int argc, char** argv) this will print out "Error occured at i = 52 & j = 99." */ - /////////////////////////////////////// // Typecasting /////////////////////////////////////// @@ -386,7 +380,6 @@ int main (int argc, char** argv) // (%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 @@ -432,7 +425,6 @@ int main (int argc, char** argv) printf("%zu, %zu\n", sizeof arraythethird, 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 @@ -455,7 +447,8 @@ int main (int argc, char** argv) int size = 10; int *my_arr = malloc(sizeof(int) * size); // Add an element to the array - my_arr = realloc(my_arr, ++size); + size++; + my_arr = realloc(my_arr, sizeof(int) * size); my_arr[10] = 5; // Dereferencing memory that you haven't allocated gives @@ -518,6 +511,7 @@ void str_reverse(char *str_in) str_in[len - ii - 1] = tmp; } } +//NOTE: string.h header file needs to be included to use strlen() /* char c[] = "This is a test."; @@ -578,8 +572,6 @@ void testFunc2() { } //**You may also declare functions as static to make them private** - - /////////////////////////////////////// // User-defined types and structs /////////////////////////////////////// @@ -696,6 +688,7 @@ typedef void (*my_fnp_type)(char *); "%o"; // octal "%%"; // prints % */ + /////////////////////////////////////// // Order of Evaluation /////////////////////////////////////// @@ -722,14 +715,14 @@ typedef void (*my_fnp_type)(char *); /******************************* Header Files ********************************** -Header files are an important part of c as they allow for the connection of c -source files and can simplify code and definitions by seperating them into -seperate files. +Header files are an important part of C as they allow for the connection of C +source files and can simplify code and definitions by separating them into +separate files. -Header files are syntactically similar to c source files but reside in ".h" -files. They can be included in your c source file by using the precompiler +Header files are syntactically similar to C source files but reside in ".h" +files. They can be included in your C source file by using the precompiler command #include "example.h", given that example.h exists in the same directory -as the c file. +as the C file. */ /* A safe guard to prevent the header from being defined too many times. This */ @@ -760,12 +753,12 @@ enum traffic_light_state {GREEN, YELLOW, RED}; /* Function prototypes can also be defined here for use in multiple files, */ /* but it is bad practice to define the function in the header. Definitions */ -/* should instead be put in a c file. */ +/* should instead be put in a C file. */ Node createLinkedList(int *vals, int len); -/* Beyond the above elements, other definitions should be left to a c source */ -/* file. Excessive includeds or definitions should, also not be contained in */ -/* a header file but instead put into separate headers or a c file. */ +/* Beyond the above elements, other definitions should be left to a C source */ +/* file. Excessive includes or definitions should, also not be contained in */ +/* a header file but instead put into separate headers or a C file. */ #endif /* End of the if precompiler directive. */ @@ -782,8 +775,8 @@ If you have a question, read the [compl.lang.c Frequently Asked Questions](http: 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 style](https://www.kernel.org/doc/Documentation/CodingStyle). +[Linux kernel coding style](https://www.kernel.org/doc/Documentation/process/coding-style.rst). 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 +[1] [Why isn't sizeof for a struct equal to the sum of sizeof of each member?](http://stackoverflow.com/questions/119123/why-isnt-sizeof-for-a-struct-equal-to-the-sum-of-sizeof-of-each-member) |