Sunday, July 23, 2006

C Programming

Sample C program

main()

{ int i;

printf("\t # \t\t Square\n");

for (i=0; i<=25;++i) printf("\t %d \t\t\t %d \n",i,square_root(i)); } square_root(int i) { return i*i; }


Compiling our sample c program using the GNU's GCC (g++) compiler

gcc test.c


or using the Sun's CC compiler

cc test.c


By default the program will be compiled to a.out We can even specify the output file by using the -o option

[root@srv31 c]# cc -o test test.c
[root@srv31 c]# ls
a.out test test.c
[root@srv31 c]# ./test
# Square
0 0
1 1
2 4
3 9
4 16
5 25
6 36
7 49
8 64
9 81
10 100
11 121
12 144
13 169
14 196
15 225
16 256
17 289
18 324
19 361
20 400
21 441
22 484
23 529
24 576
25 625

You can also define functions (and create libraries) in separate / generic files and then include them using the following syntax

cc -o test test.c myfunction.c


Using math library (e.g. taken from link below)

#include

main()

{ int i;

printf("\t Number \t\t Square Root of Number\n\n");

for (i=0; i<=360; ++i)
printf("\t %d \t\t\t %d \n",i, sqrt((double) i));

}


Compiling it:

[root@srv31 c]# vi math.c
[root@srv31 c]# cc -o math2 math.c
/tmp/ccssZM3h.o(.text+0x4a): In function `main':
: undefined reference to `sqrt'
collect2: ld returned 1 exit status
[root@srv31 c]# cc -o math2 math.c -lm


For more information, read the Linux Programmer's Manual or visit these sites:

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