View Compilation Error

0_0_31547511_4872.c: In function 'main':
0_0_31547511_4872.c:7:3: error: 'c' undeclared (first use in this function)
   c=a+b;
   ^
0_0_31547511_4872.c:7:3: note: each undeclared identifier is reported only once for each function it appears in