Get absolute value in C lang
Get absolute value of argument.
Use abs() for integer, use fabs() for decimal.
get_absolute_value.c 
#include <stdio.h>
#include <math.h>

int main(void) {
  // Get absolute value of integer
  printf("Absolute value of  5 is %d\n", abs(5));
  printf("Absolute value of -5 is %d\n", abs(-5));

  // Get absolute value of float
  printf("Absolute value of  5.5 is %f\n", fabs(5.5));
  printf("Absolute value of -5.5 is %f\n", fabs(-5.5));

  return 0;
}
Result 
$ gcc get_absolute_value.c -o get_absolute_value
$ ./get_absolute_value
Absolute value of  5 is 5
Absolute value of -5 is 5
Absolute value of  5.5 is 5.500000
Absolute value of -5.5 is 5.500000