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- Question
What is the purpose of "rb" in fopen() function used below in the code?
FILE *fp; fp = fopen("source.txt", "rb");
Options- A. open "source.txt" in binary mode for reading
- B. open "source.txt" in binary mode for reading and writing
- C. Create a new file "source.txt" for reading and writing
- D. None of above
- Correct Answer
- open "source.txt" in binary mode for reading
ExplanationThe file source.txt will be opened in the binary mode.
Input / Output problems
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- 1. Which files will get closed through the fclose() in the following program?
#include<stdio.h> int main() { FILE *fs, *ft, *fp; fp = fopen("A.C", "r"); fs = fopen("B.C", "r"); ft = fopen("C.C", "r"); fclose(fp, fs, ft); return 0; }
Options- A. "A.C" "B.C" "C.C"
- B. "B.C" "C.C"
- C. "A.C"
- D. Error in fclose() Discuss
Correct Answer: Error in fclose()
Explanation:
Extra parameter in call to fclose().- 2. In a file contains the line "I am a boy\r\n" then on reading this line into the array str using fgets(). What will str contain?
Options- A. "I am a boy\r\n\0"
- B. "I am a boy\r\0"
- C. "I am a boy\n\0"
- D. "I am a boy" Discuss
Correct Answer: "I am a boy\n\0"
Explanation:
Declaration: char *fgets(char *s, int n, FILE *stream);fgets reads characters from stream into the string s. It stops when it reads either n - 1 characters or a newline character, whichever comes first.
Therefore, the string str contain "I am a boy\n\0"
- 3. To print out a and b given below, which of the following printf() statement will you use?
#include<stdio.h> float a=3.14; double b=3.14;
Options- A. printf("%f %lf", a, b);
- B. printf("%Lf %f", a, b);
- C. printf("%Lf %Lf", a, b);
- D. printf("%f %Lf", a, b); Discuss
Correct Answer: printf("%f %lf", a, b);
Explanation:
To print a float value, %f is used as format specifier.To print a double value, %lf is used as format specifier.
Therefore, the answer is printf("%f %lf", a, b);
- 4. Out of fgets() and gets() which function is safe to use?
Options- A. gets()
- B. fgets() Discuss
Correct Answer: fgets()
Explanation:
Because, In fgets() we can specify the size of the buffer into which the string supplied will be stored.- 5. To scan a and b given below, which of the following scanf() statement will you use?
#include<stdio.h> float a; double b;
Options- A. scanf("%f %f", &a, &b);
- B. scanf("%Lf %Lf", &a, &b);
- C. scanf("%f %Lf", &a, &b);
- D. scanf("%f %lf", &a, &b); Discuss
Correct Answer: scanf("%f %lf", &a, &b);
Explanation:
To scan a float value, %f is used as format specifier.To scan a double value, %lf is used as format specifier.
Therefore, the answer is scanf("%f %lf", &a, &b);
- 6. Consider the following program and what will be content of t?
#include<stdio.h> int main() { FILE *fp; int t; fp = fopen("DUMMY.C", "w"); t = fileno(fp); printf("%d\n", t); return 0; }
Options- A. size of "DUMMY.C" file
- B. The handle associated with "DUMMY.C" file
- C. Garbage value
- D. Error in fileno() Discuss
Correct Answer: The handle associated with "DUMMY.C" file
Explanation:
fp = fopen("DUMMY.C", "w"); A file DUMMY.C is opened in write mode and returns the file pointer to fpt = fileno(fp); returns the handle for the fp stream and it stored in the variable t
printf("%d\n", t); It prints the handle number.
- 7. What does fp point to in the program?
#include<stdio.h> int main() { FILE *fp; fp=fopen("trial", "r"); return 0; }
Options- A. The first character in the file
- B. A structure which contains a char pointer which points to the first character of a file.
- C. The name of the file.
- D. The last character in the file. Discuss
Correct Answer: A structure which contains a char pointer which points to the first character of a file.
Explanation:
The fp is a structure which contains a char pointer which points to the first character of a file.- 8. On executing the below program what will be the contents of 'target.txt' file if the source file contains a line "To err is human"?
#include<stdio.h> int main() { int i, fss; char ch, source[20] = "source.txt", target[20]="target.txt", t; FILE *fs, *ft; fs = fopen(source, "r"); ft = fopen(target, "w"); while(1) { ch=getc(fs); if(ch==EOF) break; else { fseek(fs, 4L, SEEK_CUR); fputc(ch, ft); } } return 0; }
Options- A. r n
- B. Trh
- C. err
- D. None of above Discuss
Correct Answer: Trh
Explanation:
The file source.txt is opened in read mode and target.txt is opened in write mode. The file source.txt contains "To err is human".Inside the while loop,
ch=getc(fs); The first character('T') of the source.txt is stored in variable ch and it's checked for EOF.
if(ch==EOF) If EOF(End of file) is true, the loop breaks and program execution stops.
If not EOF encountered, fseek(fs, 4L, SEEK_CUR); the file pointer advances 4 character from the current position. Hence the file pointer is in 5th character of file source.txt.
fputc(ch, ft); It writes the character 'T' stored in variable ch to target.txt.
The while loop runs three times and it write the character 1st and 5th and 11th characters ("Trh") in the target.txt file.
- 9. Which of the following operations can be performed on the file "NOTES.TXT" using the below code?
FILE *fp; fp = fopen("NOTES.TXT", "r+");
Options- A. Reading
- B. Writing
- C. Appending
- D. Read and Write Discuss
Correct Answer: Read and Write
Explanation:
r+ Open an existing file for update (reading and writing).- 10. What will be the output of the program?
#include<stdio.h> int fun(int **ptr); int main() { int i=10; const int *ptr = &i; fun(&ptr); return 0; } int fun(int **ptr) { int j = 223; int *temp = &j; printf("Before changing ptr = %5x\n", *ptr); const *ptr = temp; printf("After changing ptr = %5x\n", *ptr); return 0; }
Options- A. Address of i
Address of j - B. 10
223 - C. Error: cannot convert parameter 1 from 'const int **' to 'int **'
- D. Garbage value Discuss
Correct Answer: Error: cannot convert parameter 1 from 'const int **' to 'int **'
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- 1. Which files will get closed through the fclose() in the following program?