C Aptitude Questions with Answers Part 22

1)

void pascal f(int i,int j,int k) { 
   printf(“%d %d %d”,i, j, k);  
} 
void cdecl f(int i,int j,int k) { 
   printf(“%d %d %d”,i, j, k);  
} 
main() {
   int i=10; 
   f(i++,i++,i++); 
   printf(" %d\n",i); 
   i=10; 
   f(i++,i++,i++); 
   printf(" %d",i); 
} 

Answer:
10 11 12 13
12 11 10 13
Explanation:
Pascal argument passing mechanism forces the arguments to be called from left to right. cdecl is the normal C argument passing mechanism where the arguments are passed from right to left.

2). What is the output of the program given below

main() {
       signed char i=0; 
       for(;i>=0;i++) ; 
       printf("%d\n",i); 
    } 

Answer
-128
Explanation
Notice the semicolon at the end of the for loop. THe initial value of the i is set to 0. The inner loop executes to increment the value from 0 to 127 (the positive range of char) and then it rotates to the negative value of -128. The condition in the for loop fails and so comes out of the for loop. It prints the current value of i that is -128.

3)

main() {
       unsigned char i=0;
       for(;i>=0;i++) ; 
       printf("%d\n",i); 
    } 

Answer
infinite loop
Explanation
The difference between the previous question and this one is that the char is declared to be unsigned. So the i++ can never yield negative value and i>=0 never becomes false so that it can come out of the for loop.

4)

main() {
       char i=0; 
       for(;i>=0;i++) ; 
       printf("%d\n",i);
 } 

Answer:
Behavior is implementation dependent.
Explanation:
The detail if the char is signed/unsigned by default is implementation dependent. If the implementation treats the char to be signed by default the program will print –128 and terminate. On the other hand if it considers char to be unsigned by default, it goes to infinite loop.

You can write programs that have implementation dependent behavior. But dont write programs that depend on such behavior. 

5) Is the following statement a declaration/definition. Find what does it mean?

int (*x)[10]; 

Answer
Definition.
  x is a pointer to array of(size 10) integers.
Apply clock-wise rule to find the meaning of this definition.