c

Complete

Summary

Operator precedence

1.  ++(suffix) --(suffix) () [] . ->
2.  ++(prefix) --(prefix) ! ~ (type)(cast) *(dereference) &(address-of) sizeof
3.  * / %
4.  + -
5.  << >>
6.  < <= > >=
7.  == !=
8.  &(logical)
9.  ^
10. |
11. &&
12. ||
13. ?: (ternary)
14. = += -= *= /= %= <<= >>= &= ^= |=
15. ,

Preprocessor directives

// importing header files/libraries
#include <stdio.h>

// macros 
#define PI 3.142 // use all CAPs for macro

note the absence of ’;’ in the preprocessor directives

Format specifiers

Placeholder	Variable Type	Function Use
%c	char	printf / scanf
%d	int	printf / scanf
%f	float or double	printf
%f	float	scanf
%lf	double	scanf
%e	float or double	printf (for scientific notation)

%5d -> integer with width of 5, right justified
%8.3f -> real number with width of 8 and 3 decimal places, right justified

Escape sequences

Escape sequence	Meaning	Result
\n	New line	Subsequent output will appear on the next line
\t	Horizontal tab	Move to the next tab position on the current line
\“	Double quote	Display a double quote “
%%	Percent	Display a percent character %

see Learn X in Y minutes: C for complete guide to C

Concept

Compilation

bash

// compiling to executable file
gcc test.c -o test

// compiling with all warnings
gcc -Wall test.c

Variables

int x; // initialization
x = 2; // declaration

int y = 2; // initialization and declaration

Command line arguments

pass in command line arguments
argc - number of command line args
argv - array of the argument strings, separated by space
envp - array of environment variables

int main (int argc, char *argv[], char *envp[]) {
	int i;
	
	for (i = 0; i < argc; i++) {
		printf("Arg %d: %s\n",i, argv[i] );
	}
	
	i=0;
	while(vp[i] != NULL) {
		printf("Env %d: %s\n", i, vp[i]);
		i++;
	}  
	
	return 0; 
}

Application

Macros

#define PI 3.142

int main(void) {
	...
	areaCircle = PI * radius * radius;
	volCone = PI * radius * radius * height / 3.0;
}

// becomes this before compliation

int main(void) {
	...
	areaCircle = 3.142 * radius * radius;
	volCone = 3.142 * radius * radius * height / 3.0;
}