Selected C formats

/* enclose comments within slash-star and star-slash */

#include <stdio.h> Replace line with contents of system header file

STDIO.H.

int main( int argc, char *argv [] ) All programs start execution with the

function main. argc contains the

number of command line arguments. argv is an array

of pointers to those arguments.

char c; Single byte-size variable.

char msg[]="HELP\n"; Initialized array; 6 characters (last is 0).

double big; Double-precision floating-point variable.

float matrix[10][50]; Two-dimension array.

int i,j,k; Three two-byte-sized variables.

long int sum; One four-byte-sized variables.

void myproc(void); Declare prototype function without a return value.

x = 1; Assignment expression. Terminate simple statements

with semicolon.

; It is legal to have a statement do nothing.

{ tmp=a; a=b; b=tmp; } Surround compound statements with braces where a

simple statement would be allowed.

break; Terminate smallest enclosing do, for, switch or

while.

continue; Start the next cycle of a loop.

do c=getchar(); while (c==' '); Perform statement until condition is false.

Always executes at least once.

for ( i=0; i<MAX; a[i++]=c ) Initialize once, then while condition is true do statement,

c=getchar(); then do increment. Initialization will occur, but

statement will not be executed if condition starts out

false.

if (a<0) a = -a; Perform statement if condition is true.

else printf( "was plus\n" ); Optional else after if.

return; Exit function with return type void.

return a+c; Exit function and return value of optional expression to

caller.

switch (getchar()) { Evaluate expression and perform appropriate case.

case 'X': exit(0);

case 'H': help(); break; If no break, falls into next case.

case 'A': case 'B': a++; break; Multiple cases allowed.

default: printf("Try again.\n"); Default if no case matched.

}

while (i<MAX) a[i++]=0; Perform statement while condition is true. Statement

will not be executed if condition starts false.

Selected printf escape sequences

%% percent sign

%c single ascii character

%d signed decimal integer (%ld for long)

%e scientific notation with lower case e

%f fixed point notation

%g use %e or %f, whichever is shorter

%i general integer conversion (%li for long)

%o unsigned octal integer (%lo for long)

%s string

%u unsigned decimal integer (%lu for long)

%x unsigned hexadecimal integer with lower case abcdef (%lx for long)

Precedence of Selected Operators

Primary expression

[] array element () function call

Unary operators

& address - minus ! logical not ++ inc -- dec sizeof ()cast

Binary operators

* multiply / divide % modulus

+ add - subtract

< less than > greater than <= less than or equal >= greater than or equal

== equals != not equals

&& logical and

|| logical or

Conditional expression

condition ? true : false

Assignment operators

= *= /= %= += -=