No matter what programming language, in addition to a comprehensive collection of variable types / forms, a robust collection of logic test statements is very important. From those logic primitives, comes looping, branching constructs, which we will see very soon.
- Open both terminal window & text editor, and navigate to your work subdirectory.
- Save the block of code below as 'main.c'.
- (copy from 'pgm4' the 'goc' text file, make it executable.)
- Compile using "./goc main.c pgm5", then run './pgm5'.
- Notice when invoking with "./pgm5 red rose", the two command-line parameters are ignored by the program
/* 'pgm5' source */
#include <stdio.h>
// we can leave these command line variables present, and NOT use them
int main(int argc, char *argv[]) {
int qnty_ducks;
int qnty_chickens;
float day_temp;
float night_temp;
// initialization of variables
qnty_ducks = 13; qnty_chickens = 47; // OK to have more than one statement per line
day_temp = 43.7; night_temp = 22.3;
// show the initialized variables
printf("\n");
printf("qnty_ducks = %d, qnty_chickens = %d\n", qnty_ducks, qnty_chickens);
printf("day_temp = %.1f, night_temp = %.1f\n\n", day_temp, night_temp);
// now evaluate and display conclusions
printf("So, what does the data at hand mean??\n");
if (qnty_chickens > qnty_ducks) // test for qnty_chickens GREATER THAN qnty_ducks
printf("Time to make soup for everybody!\n"); // if test TRUE, print this
else
printf("Can't wait for those ducks to leave...\n"); // if test FALSE, print this
if (night_temp < day_temp) // test for night_temp LESS THAN day_temp
printf("The temperatures today seem sensible\n"); // if test TRUE, print this
printf("\n");
return(0);
}
By now, we've seen 4 ways to test logic: '==' (is equal?), '!=' (is not equal?) '<' (is the left item less than the right item?) and '>' (is the left item greater than the right item?).