C Programming Interview Questions - Ungetc

This section on C programming interview questions and answers focuses on “Ungetc Function”. One shall practice these interview questions to improve their C programming skills needed for various interviews (campus interviews, walkin interviews, company interviews), placements, entrance exams and other competitive exams. These questions can be attempted by anyone focusing on learning C Programming language. They can be a beginner, fresher, engineering graduate or an experienced IT professional. Our C programming interview questions come with detailed explanation of the answers which helps in better understanding of C concepts.

Here is a listing of C programming interview questions on “Ungetc Function” along with answers, explanations and/or solutions:

1. ungetc can be used only with getc.
a) true
b) false
c) depends on the standard
d) depends on the platform
View Answer

Answer: b
Explanation: None.

2. Which character of pushback is guaranteed per file?
a) True
b) False
c) Depends on the compiler
d) Depends on the platform
View Answer

Answer: a
Explanation: None.

3. What is the output of this C code?

```
    #include <stdio.h>
```
```
    int main()
```
```
    {
```
```
        int n;
```
```
        scanf("%d", &n);
```
```
        ungetc(n, stdin);
```
```
        scanf("%d", &n);
```
```
        printf("%d\n", n);
```
```
        return 0;
```
```
    }
```

a) Compile time error
b) Whatever is typed by the user first time
c) Whatever is typed by the user second time
d) Undefined behaviour
View Answer

Answer: b
Explanation: None.

4. What is the output of this C code?

```
    #include <stdio.h>
```
```
    int main()
```
```
    {
```
```
        char n[20];
```
```
        fgets(n, 19, stdin);
```
```
        ungetc(n[0], stdin);
```
```
        scanf("%s", n);
```
```
        printf("%s\n", n);
```
```
        return 0;
```
```
    }
```

a) Compile time error
b) Whatever string user types second time
c) Whatever string user types first time
d) first character of whatever user types first time and whatever user types second time
View Answer

Answer: d
Explanation: None.

5. What is the output of this code considering user typed jkl?

```
    #include <stdio.h>
```
```
    int main()
```
```
    {
```
```
        char n[20];
```
```
        fgets(n, 19, stdin);
```
```
        ungetc(n[0], stdin);
```
```
        printf("%s\n", n);
```
```
        return 0;
```
```
    }
```

a) jkl
b) kl
c) Undefined behaviour
d) jk
View Answer

Answer: a
Explanation: None.

6. How many characters for pushback is guaranteed per file while using

ungetc(c, fp);

a) Only 1 character
b) Characters within 1 word
c) Characters within 1st new-line
d) All characters upto NULL character
View Answer

Answer: a
Explanation: None.

7. Which of the following is the correct syntax for calling function ungetc?

Assume int c and FILE *fp

a) ungetc(c,*fp);
b) ungetc(c, fp);
c) ungetc(fp, c);
d) ungetc(*fp,c);
View Answer

Answer: b
Explanation: None.

8. ungetc is used
a) to get a char
b) to get an int
c) to push a character back to file
d) nothing
View Answer

Answer: c
Explanation: None.

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