使用gcc编译C程序

Question

I am following an example from CUNY and I have never done anything with C before so I probably don't know what I am doing.

Consider the program below.

1. Do I need a shebang line for C code written in emacs?

2. When I go to compile using the line gcc -g -o forwardadding forwardadding.c I am hit with the message:

    forwardadding.c:9:17: error: expected expression before '<' token 

3. Once I get the code compiles, I can use gdb to debug and run the code corrrect?

The code:

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

main()
{
    float sum, term;
    int i;
    sum = 0.0;
    for( i = 1; < 10000000; i++)
    {
        term = (float) i;
        term = term * term;
        term = 1 / term;
        sum += term;
    }
    printf("The sum is %.12f\n", sum);
}

Answer 1

1. No shebang is needed. You could add an Emacs mode line comment.

2. The for loop should be:

    for (i = 1; i < 10000000; i++) 

   Your code is missing the second i .

3. Yes, you can use GDB once you've got the code compiling.

You'd get a better answer to the mathematics if you counted down from 10,000,000 than by counting up to 10,000,000. After about i = 10000 , the extra values add nothing to the result.

Please get into the habit of writing C99 code. That means you should write:

int main(void)

with the return type of int being required and the void being recommended.

Answer 2

You need to put a variable in the for loop for a complete expression (which is probably line 9...)

for( i = 1; < 10000000; i++)

change to this

for( i = 1; i < 10000000; i++)

Answer 3

You are missing an an i . Just correct that as Jonathan Leffler has suggested and save your file. Open your terminal and just use this to compile your code gcc your_file_name.c and your code compiles next to run the code that just compiled type ./a.out and your program runs and shows you the output.