1.6.1 if

The if statement evaluates an expression. If that expression is true, then a statement is executed. If an else clause is given and if the expression is false, then the else's statement is executed.

Syntax:

if( expression ) statement1;

or

if( expression ) statement1;
else statement2 ;

Examples:


if(loop<3) counter++;

if(x==y)
  x++;
else
  y++;

if(z>x)
 {
  z=5;
  x=3;
 }
else
 {
  z=3;
  x=5;
 }

1.6.2 switch

A switch statement allows a single variable to be compared with several possible constants. If the variable matches one of the constants, then a execution jump is made to that point. A constant can not appear more than once, and there can only be one default expression.

Syntax:

switch ( variable )
 {
  case const:
   statements...;
  default:
   statements...;
 }

Examples:


switch(betty)
 {
  case 1:
    printf("betty=1\n");
  case 2:
    printf("betty=2\n");
    break;
  case 3:
    printf("betty=3\n");
    break;
  default:
    printf("Not sure.\n");
 }

If betty is 1, then two lines are printed: betty=1 and betty=2. If betty is 2, then only one line is printed: betty=2. If betty=3, then only one line is printed: betty=3. If betty does not equal 1, 2, or 3, then "Not sure." is printed.

1.6.3 while

The while statement provides an iterative loop.
Syntax:

while( expression ) statement...

statement is executed repeatedly as long as expression is true. The test on expression takes place before each execution of statement.
Examples:


while(*pointer!='j') pointer++;

while(counter<5)
 {
  printf("counter=%i",counter);
  counter++;
 }

1.6.4 do

The do...while construct provides an iterative loop.

Syntax:

do statement... while( expression );

statement is executed repeatedly as long as expression is true. The test on expression takes place after each execution of statement.

Examples:


do {
  betty++;
  printf("%i",betty);
} while (betty<100);

1.6.5 for

The for statement allows for a controlled loop.

Syntax:

for( expression1 ; expression2 ; expression3 ) statement...

expression1 is evaluated before the first iteration. After each iteration, expression3 is evaluated. Both expression1 and expression3 may be ommited. If expression2 is ommited, it is assumed to be 1. statement is executed repeatedly until the value of expression2 is 0. The test on expression2 occurs before each execution of statement.

Examples:

for(loop=0;loop<1000;loop++)
  printf("%i\n",loop);

Prints numbers 0 through 999.

for(x=3, y=5; x<100+y; x++, y--)
 {
  printf("%i\n",x);
  some_function();
 }

Prints numbers 3 through 53. some_function is called 51 times.

1.6.6 goto

The goto statement transfers program execution to some label within the program.

Syntax:

goto label;
....
label:

Examples:

goto skip_point;
printf("This part was skipped.\n");
skip_point:
printf("Hi there!\n");

Only the text "Hi there!" is printed.

1.6.7 continue

The continue statement can only appear in a loop body. It causes the rest of the statement body in the loop to be skipped.

Syntax:

continue;

Examples:

for(loop=0;loop<100;loop++)
 {
  if(loop==50)
    continue;
  printf("%i\n",loop);
 }

The numbers 0 through 99 are printed except for 50.

joe=0;
while(joe<1000)
 {
 for(zip=0;zip<100;zip++)
  {
   if(joe==500)
    continue;
   printf("%i\n",joe);
  }
 joe++;
}

Each number from 0 to 999 is printed 100 times except for the number 500 which is not printed at all.

1.6.8 break

The break statement can only appear in a switch body or a loop body. It causes the execution of the current enclosing switch or loop body to terminate.

Syntax:

break;

Examples:

switch(henry)
 {
 case 1: print("Hi!\n");
         break;
 case 2: break;
 }

If henry is equal to 2, nothing happens.

for(loop=0;loop<50;loop++)
 {
  if(loop==10)
    break;
  printf("%i\n",loop);
 }

Only numbers 0 through 9 are printed.

1.6.9 return

The return statement causes the current function to terminate. It can return a value to the calling function. A return statement can not appear in a function whose return type is void. If the value returned has a type different from that of the function's return type, then the value is converted. Using the return statement without an expression creates an undefined result. Reaching the } at the end of the function is the same as returning without an expression.

Syntax:

return expression;

Examples:

int alice(int x, int y)
 {
  if(x<y)
    return(1);
  else
    return(0);
}

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