Functions and bounded loops

The idea

Enter with initialized variables and arithmetic. A function receives arguments through parameters and returns a result with return. Parameters passed by value are separate objects: changing an integer parameter does not change the caller’s integer. Give each function a narrow job, and state which inputs it accepts. The example below assumes a small nonnegative limit so every accumulated value fits in int.

A for loop combines initialization, a continuation test, and an update. The test is checked before each iteration, so a false first test produces no iterations. Trace a short table containing the loop counter and accumulator rather than trying to infer the final number from punctuation. For larger or untrusted inputs, revisit overflow and termination instead of assuming that a loop which works on three values is safe for every integer.

#include <stdio.h>
int sumThrough(int limit){int total=0; for(int i=1;i<=limit;i++) total+=i; return total;}
int main(void){printf("%d\n",sumThrough(4));}

10

The counter takes 1, 2, 3, and 4. The initial zero also makes a limit of zero return zero without entering the loop.