GATE CS 2012 Q48 — Programming in C

To find the output of the given C program, let's trace the execution step-by-step, keeping track of the scope and lifetime of the variables.

1. Global Variables

The global variables are declared as:

int a, b, c = 0;

Since they are global, they are initialized to 0 by default:

• Global a = 0
• Global b = 0
• Global c = 0

2. Execution of main()

• static int a = 1;: This declares a static local variable a inside main() (let's call it main_a), initialized to 1.

First Call to prtFun():

• Inside prtFun(), static int a = 2; declares a static local variable (let's call it prt_a), initialized to 2.
• int b = 1;: A local auto variable b is initialized to 1.
• a += ++b;:
  • ++b is a pre-increment operation, so b becomes 2.
  • prt_a += 2 updates prt_a to $2 + 2 = 4$.
• printf(" \n %d %d ", a, b); prints the local prt_a and local b:
  4 2

Back in main():

• a += 1;: This updates the local static variable main_a from 1 to 2.

Second Call to prtFun():

• Since prt_a is static, it retains its previous value of 4.
• The local auto variable b is re-initialized to 1.
• a += ++b;:
  • ++b increments b to 2.
  • prt_a += 2 updates prt_a to $4 + 2 = 6$.
• printf(" \n %d %d ", a, b); prints:
  6 2

Final Print in main():

• printf(" \n %d %d ", a, b);:
  • a refers to the local static variable main_a, which has the value 2.
  • b is not declared locally in main(), so it refers to the global variable b, which is 0.
• This prints:
  2 0

Conclusion

The generated output is:

4  2
6  2
2  0

This corresponds to Option C.