Local variables

You can declare variables at the start of the function body:

/* return the harmonic mean of three numbers */ float my_mean(float a, float b, float c) { float t; t = 1.0/a; t = t + 1.0/b; t = t + 1.0/c; return 3.0/t; }

The variable t declared here is only visible in the body of the function; any other variable called t declared elsewhere will not be effected by calls to my_mean:

float t; /* this is visible everywhere (a `global' variable) */ float my_mean(float a, float b, float c) { float t; /* in the body of the function, references to t effect the local variable t, declared on the line above */ /* .. */ } int main(void) { float p; t = 1; p = my_mean(3.0, 4.0, 5.0); /* t still equals one */ }

Each time the function is called, memory for the local variable t will be allocated afresh, so its value will not be preserved between calls. If you do want the value to be preserved, use static.