File Operations in C Programming : 2 Marks Definition Answers

2 Marks Definition Answers

 

• Files are comprised of one or more records. Each record in a file should describe a unique collection of fields. Files can be used to store all types of information, such as student or employee data. Data files are normally associated with various database processes in which information can be managed in non‒volatile states, such as a disk drive.

 

• Bits are also known as binary digits, bits are the smallest value in a data file. Each bit value can only be a 0 or 1.

 

• Bytes provide the next step in the data file. Bytes are most commonly made up of eight bits and used to store a single character, such as a number, a letter, or any other character found in a character set.

 

• In database or data‒file, groupings of characters are most commonly referred to as fields.

 

• Records are logical groupings of fields that comprise a single row of information or record. Each field in a record describes the record's attributes. When the data is stored in a file, it is stored permanently.

 

• This means that even through the computer is switched off, the data cannot removed from the memory since the file is stored on perminant memory. This file data can be utilized as and when required.

 

• It is possible to update the data. For example, we can add new data to the existing file, delete unnecessary data from the file and modify the available data of the file

 

• Files are highly useful to store huge amount of data.

 

• Text: An organized sequence of characters. A text stream allows certain character translations, depending on the environment. As a result, there may not be a one‒to‒one relationship between what is written and what is read.

 

• Binary: A sequence of bytes stored as they are written and read as they are stored. These differ from text streams because there is no translation of characters and these are read in the same way in which they are stored.

 

• A data file must be opened before it can be created or processed, this associates the file name with buffer area.

Syntax:

FILE *fp;

fp=fopen("filename", "mode");

 

• When an 'r' mode used, the file is opened for reading, a'w' is used to indicate a file to be used for writing, and an a indicates that you desire to append additional data to the data already in an existing file.

 

• A file must be closed after all the operation of the file have been completed.

Syntax: fclose(file‒pointer);

 

• A data file must be created before it can be processed. In two ways a stream‒ oriented data file can be created. One is using a text editor or a word processor to create the file directly.

 

• Once the file is in opened mode, as usual we can write() method to append the strings to the file. After writing the data, without closing the file, we can read strings from the file of all, we should place the file handler to the beginning of the file using seek() method as:

Syntax: f.seek(offset, from where)

 

• The file object provides a set of access methods to make our lives easier. We would see how to use read() and write() methods to read and write files

 

• The operating system (os) module has a sub module by the name 'path' that contains a method isfile(). This method can be used to know whether a file that we are opening really exists or not.

 

• When you are searching through data in a file, it is a very common pattern to read through a file, ignoring most of the lines and only processing lines which meet a particular condition. We can combine the pattern for reading a file with string methods to build simple search mechanisms.

 

• Directly going to any byte in the binary file is called random accessing. This is possible by moving the file pointer to any location in the file and then performing reading or writing operations on the file as required.

 

• Random accessing is also possible using mmap (memory mapped file) module.

 

• Zipping and unzipping of a fine can be done using ZipFile class of zipfile module.

 

• The error function reports the statistics of the file indicated. It also takes a file pointer as its argument and returns a non zero integer, if an error has been detected upto that point, during processing otherwise it returns zero

 

• perror() is a standard library function which prints the error messages specified by the complier.

 

MULTIPLE CHOICE QUESTIONS

 

1. The first and second arguments of fopen are

a) A character string containing the name of the file & the second argument is the mode.

b) A character string containing the name of the user & the second argument is the mode.

c) A character string containing file poniter & the second argument is the mode.

d) None of the mentioned of the mentioned

 

2. For binary files, a ________ must be appended to the mode string.

a) Nothing

b) "b"

c) "binary"

d) "01"

 

3. If there is any error while opening a file, fopen will return

a) Nothing

b) EOF

c) NULL

d) Depends on compiler

 

4. Which is true about getc.getc returns?

a) The next character from the stream referred to by file pointer

b) EOF for end of file or error

c) Both a & b

d) Nothing.

 

5. When a C program is started, O.S environment is responsible for opening file and providing pointer for that file?

a) Standard input

b) Standard output

c) Standard error

d) All of the menitoned

 

6. FILE is of type ______?

a) int type

b) char * type

c) struct type

d) None of the mentioned

 

7. What is the meant by 'a' in the following operation?

fp = fopen("Random.txt", "a");

a) Attach

b) Append

c) Apprehend

d) Add

 

8. Which type of files can't be opened using fopen()?

a) .txt

b).bin

c) .c

d) None of the mentioned

 

9. Which of the following fopen statements are illegal?

a) fp = fopen("abc.txt", "r");

b) fp = fopen("/home/user1/abc.txt", "w");

c) fp = fopen("abc", "w");

d) None of the mentioned

 

10. What does the following segment of code do?

fprintf(fp, "Copying!");

a) It writes "Copying!" into the file pointed by fp

b) It reads "Copying!" from the file and prints on display

c) It writes as well as reads "Copying!" to and from the file and prints it

d) None of the mentioned

 

11. FILE reserved word is

a) A structure tag declared in stdio.h

b) One of the basic datatypes in c

c) Pointer to the structure defined in stdio.h

d) It is a type name defined in stdio.h

 

12. What is the output of this C code?

#include <stdio.h>

int main()

{

FILE *fp = stdin;

int n;

fprintf(fp, "%d", 45);

}

a) Compilation error

b) 45

c) Nothing

d) Depends on the standard

 

 

TRUE/FALSE

 

1. If there is any error while opening a file, fopen will return null.

True/False

2. Byte is the smallest value in a data file

True/False

3. Grouping of characters are also called as fields

True/False

4. Records are groupings of fields that comprise of double row of information or record

True/False

5. Files are comprised of only one record.

True/False

6. A stream is a continuous series of bytes that flow into or out of program

True/False

7. fprintf and fscanf are not similar to scanf and printf.

True/False

8. The sequential access is disadvantage.

True/False

9. ftell() function is used to specify the current position of the file.

True/False

10. FILE is of static type.

True/False

11. The FILE type in C is a basic data type like int or char.

True/False

12. The fopen() function returns NULL if there is an error opening the file.

True/False

13. The "w" mode in fopen() truncates the file if it already exists.

True/False

14. fprintf() can only be used to write strings to a file.

True/False

15. fclose() should be called for every file opened using fopen() to release system resources.

True/False

16. feof() returns true if the end‒of‒file indicator is set for the specified stream.

True/False

17. fseek() can be used to move the file pointer to any position within a file, including before the beginning of the file.

True/False

18. Binary files are always opened with the "b" modifier (e.g., "rb", "wb", "ab").

True/False

19. rewind() is preferred over fseek() for repositioning the file pointer to the beginning of a file because it provides error checking.

True/False

20. It is safe to perform file operations on a file pointer that has been closed using fclose().

True/False