Control Instructions problems
- 1. Point out the error, if any in the for loop.
#include<stdio.h> int main() { int i=1; for(;;) { printf("%d\n", i++); if(i>10) break; } return 0; }
Options- A. There should be a condition in the for loop
- B. The two semicolons should be dropped
- C. The for loop should be replaced with while loop.
- D. No error Discuss
Correct Answer: No error
Explanation:
Step 1: for(;;) this statement will genereate infinite loop.
Step 2: printf("%d\n", i++); this statement will print the value of variable i and increement i by 1(one).
Step 3: if(i>10) here, if the variable i value is greater than 10, then the for loop breaks.
Step 2: printf("%d\n", i++); this statement will print the value of variable i and increement i by 1(one).
Step 3: if(i>10) here, if the variable i value is greater than 10, then the for loop breaks.
Hence the output of the program is
1
2
3
4
5
6
7
8
9
10
- 2. Point out the error, if any in the program.
#include<stdio.h> int main() { int P = 10; switch(P) { case 10: printf("Case 1"); case 20: printf("Case 2"); break; case P: printf("Case 2"); break; } return 0; }
Options- A. Error: No default value is specified
- B. Error: Constant expression required at line case P:
- C. Error: There is no break statement in each case.
- D. No error will be reported. Discuss
Correct Answer: Error: Constant expression required at line case P:
Explanation:
The compiler will report the error "Constant expression required" in the line case P: . Because, variable names cannot be used with case statements.
The case statements will accept only constant expression.
- 3. Point out the error, if any in the while loop.
#include<stdio.h> int main() { int i=1; while() { printf("%d\n", i++); if(i>10) break; } return 0; }
Options- A. There should be a condition in the while loop
- B. There should be at least a semicolon in the while
- C. The while loop should be replaced with for loop.
- D. No error Discuss
Correct Answer: There should be a condition in the while loop
Explanation:
The while() loop must have conditional expression or it shows "Expression syntax" error.
Example: while(i > 10){ ... }
- 4. Point out the error, if any in the program.
#include<stdio.h> int main() { int i = 1; switch(i) { printf("This is c program."); case 1: printf("Case1"); break; case 2: printf("Case2"); break; } return 0; }
Options- A. Error: No default specified
- B. Error: Invalid printf statement after switch statement
- C. No Error and prints "Case1"
- D. None of above Discuss
Correct Answer: No Error and prints "Case1"
Explanation:
switch(i) becomes switch(1), then the case 1: block is get executed. Hence it prints "Case1".
printf("This is c program."); is ignored by the compiler.
Hence there is no error and prints "Case1".
- 5. Point out the error, if any in the while loop.
#include<stdio.h> int main() { void fun(); int i = 1; while(i <= 5) { printf("%d\n", i); if(i>2) goto here; } return 0; } void fun() { here: printf("It works"); }
Options- A. No Error: prints "It works"
- B. Error: fun() cannot be accessed
- C. Error: goto cannot takeover control to other function
- D. No error Discuss
Correct Answer: Error: goto cannot takeover control to other function
Explanation:
A label is used as the target of a goto statement, and that label must be within the same function as the goto statement.
Syntax: goto <identifier> ;
Control is unconditionally transferred to the location of a local label specified by <identifier>.
Example:
#include <stdio.h>
int main()
{
int i=1;
while(i>0)
{
printf("%d", i++);
if(i==5)
goto mylabel;
}
mylabel:
return 0;
}
Output: 1,2,3,4
- 6. Which of the following errors would be reported by the compiler on compiling the program given below?
#include<stdio.h> int main() { int a = 5; switch(a) { case 1: printf("First"); case 2: printf("Second"); case 3 + 2: printf("Third"); case 5: printf("Final"); break; } return 0; }
Options- A. There is no break statement in each case.
- B. Expression as in case 3 + 2 is not allowed.
- C. Duplicate case case 5:
- D. No error will be reported. Discuss
Correct Answer: Duplicate case case 5:
Explanation:
Because, case 3 + 2: and case 5: have the same constant value 5.
- 7. Point out the error, if any in the program.
#include<stdio.h> int main() { int a = 10, b; a >=5? b=100: b=200; printf("%d\n", b); return 0; }
Options- A. 100
- B. 200
- C. Error: L value required for b
- D. Garbage value Discuss
Correct Answer: Error: L value required for b
Explanation:
Variable b is not assigned.
It should be like:
b = a >= 5 ? 100 : 200;
- 8. Point out the error, if any in the program.
#include<stdio.h> int main() { int i = 1; switch(i) { case 1: printf("Case1"); break; case 1*2+4: printf("Case2"); break; } return 0; }
Options- A. Error: in case 1*2+4 statement
- B. Error: No default specified
- C. Error: in switch statement
- D. No Error Discuss
Correct Answer: No Error
Explanation:
Constant expression are accepted in switch
It prints "Case1"
- 9. Point out the error, if any in the program.
#include<stdio.h> int main() { int a = 10; switch(a) { } printf("This is c program."); return 0; }
Options- A. Error: No case statement specified
- B. Error: No default specified
- C. No Error
- D. Error: infinite loop occurs Discuss
Correct Answer: No Error
Explanation:
There can exists a
switch statement, which has no
case.
- 10. Which of the following statements are correct about the program?
#include<stdio.h> int main() { int x = 30, y = 40; if(x == y) printf("x is equal to y\n"); else if(x > y) printf("x is greater than y\n"); else if(x < y) printf("x is less than y\n") return 0; }
Options- A. Error: Statement missing
- B. Error: Expression syntax
- C. Error: Lvalue required
- D. Error: Rvalue required Discuss
Correct Answer: Error: Statement missing
Explanation:
This program will result in error "Statement missing ;"
printf("x is less than y\n") here ; should be added to the end of this statement.
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