Novice - C assignment help

Question

1.00/5 (2 votes)

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Quote:
Each of these very short programs has something wrong with it. Explain what, and explain how to fix it. Your answers should each be two sentences or less.Hint: atof() and atoi() work and are not the problem

1.

#include <math.h>
#include <stdio.h>
#include <string.h>

int main(void) {
     char *s[80];
     int i;

     printf("Enter a number: ");
     fgets(s, 80, stdin);
     i = atoi(s);
     printf("You said %d.\n", i);
     return 0;
}

2.

#include <math.h>
#include <stdio.h>
#include <string.h>

int main(void) {
      int i;

     scanf("%d", i);
     printf("You said %d.\n", i);
     return 0;
}

3.

#include <math.h>
#include <stdio.h>
#include <string.h>

int main(void) {
     float x;

     scanf("%d", &x);
     printf("You said %d.\n", x);
     return 0;
}

4.

#include <math.h>
#include <stdio.h>
#include <string.h>
int main(void) {
     char s[80];
     float x, y;
     FILE *ofp;
     printf("Enter a number to square: ");
     fgets(s, 80, stdin);
     x = atof(s);
     y = x * x;

     ofp = fopen("math-results.txt", "w");
     fprintf(ofp, "%f squared is %f.\n", x, y);
     return 0;
}

What I have tried:

I am a novice beginning to learn so go easy on me - with the comments in the program you can see what I am attempting to do. I am not sure where to go from here.

Posted 9-Apr-21 12:44pm

Member 15078300

Updated 9-Apr-21 14:45pm

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Comments

jeron1 9-Apr-21 19:13pm

Where to go from here is to analyze each line of each program (start with #1) and see if you can't find the issue. Surely you have a book or some class notes you can use.

[no name] 9-Apr-21 20:41pm

It seems if you compare all 4 programs at the same time, you get an idea of what's wrong. There are differences where you might expect none. You can then research that difference.

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Rick York · Answer 1 · 2021-04-09T14:45:00

I'll give you hint on the first one. I'll show you the parts that are wrong but I won't tell you why.

C++

#include <math.h>
#include <stdio.h>
#include <string.h>

int main(void)
{
     char *s[80];            <--------------------------
     int i;

     printf("Enter a number: ");
     fgets(s, 80, stdin);    <--------------------------
     i = atoi(s);            <--------------------------
     printf("You said %d.\n", i);
     return 0;
}

Look at the documentation for fgets. I'll help you with that too : fgets - C++ Reference[^]. From there, it's up to you to figure out what the error is and describe it. Another hint - the last two aren't the actual error. They are effectively errors because of the first one.

This is what you need to do with the rest of them too. They involve similar errors. Except for the last one - it's a bit more subtle.