File Handling in C Programming

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Questions and Answers

What is the purpose of a preprocessor directive in C?

  • It handles memory allocation during execution.
  • It provides instructions to the compiler before actual compilation. (correct)
  • It executes code during runtime.
  • It defines the structure of data files.

What is the difference between text files and binary files?

  • Text files are typically slower to access compared to binary files. (correct)
  • Text files have larger sizes due to compression.
  • Binary files are more human-readable than text files.
  • Binary files usually contain text data in encoded format.

What does the ftell() function return in C?

  • The size of the file opened.
  • The total number of bytes in the file.
  • The next available byte to write in the file.
  • The current position of the file pointer in bytes. (correct)

What does the fseek function do when provided with SEEK_END?

<p>Moves the file pointer to a specific location from the end of the file. (D)</p> Signup and view all the answers

Which of the following statements about #ifdef and #ifndef is true?

<p>#ifdef checks if a macro is defined while #ifndef checks if a macro is not defined. (A)</p> Signup and view all the answers

What happens after the rewind() function is called on a file pointer in C?

<p>The file pointer resets to the beginning of the file. (C)</p> Signup and view all the answers

In the provided code, what will be printed after the #undef VALUE statement?

<p>This won't print as VALUE is undefined. (C)</p> Signup and view all the answers

Which statement correctly describes the behavior of the #include directive?

<p>It allows access to functions defined in other files. (A)</p> Signup and view all the answers

What does the fseek() function do in a file handling context?

<p>Moves the file pointer to a specified location. (A)</p> Signup and view all the answers

In the context of copying file content, what is checked immediately after opening the files?

<p>If the files were opened successfully. (A)</p> Signup and view all the answers

How does the program read characters from the source file during the copy operation?

<p>Using the fgetc() function. (A)</p> Signup and view all the answers

What is the purpose of the #define directive in a C program?

<p>To define macros or constants. (B)</p> Signup and view all the answers

What will happen if the source or destination files fail to open?

<p>An error message will be printed and the program will return 1. (A)</p> Signup and view all the answers

In the preprocessor directives, what does #pragma do?

<p>Specifies compiler-specific instructions. (C)</p> Signup and view all the answers

In the program that reads a specified number of records from a file, what method is incorrectly used to read a line from the file?

<p>fgetc() is used to read one character at a time. (D)</p> Signup and view all the answers

What is the significance of the buffer variable in the example that reads 10 bytes from the file?

<p>It must be declared as an array to hold multiple characters. (A)</p> Signup and view all the answers

Flashcards

What are preprocessor directives?

Instructions executed by the preprocessor before compilation. Used for tasks like including files, defining macros, and conditional compilation.

What are text files?

Files that store data in a readable format (e.g., .txt files).

What are binary files?

Files that store data in binary format, more efficient for storage but not human-readable.

What is the fseek function?

A function that moves the file pointer to a specific location in a file. It takes the file pointer, offset, and origin (SEEK_SET, SEEK_CUR, or SEEK_END) as arguments.

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What is the ftell function?

Returns the current position of the file pointer in a file, measured from the beginning in bytes.

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What is the rewind function?

Resets the file pointer to the beginning of a file.

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What is #ifdef?

Conditional compilation: Only if a macro is defined, the code within it is compiled.

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What is #undef?

Removes a macro definition.

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What is the purpose of fseek in C?

In C programming, fseek is a function that allows you to move the file pointer to a specific location within a file. It enables random access, meaning you can read or write data at any position within the file, not just sequentially.

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Explain the #include preprocessor directive.

The #include directive tells the C preprocessor to include the contents of a specified file in your source code before compilation. This is crucial for using standard library functions and headers.

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What does the #define preprocessor directive do?

The #define directive allows you to define symbolic constants or macros in your C code. These can be used to give meaningful names to values or to create short-hand code replacements.

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What are preprocessor directives in C language?

A preprocessor directive is an instruction that is executed before the actual compilation of your C code. It's like a set of commands that tell the compiler how to prepare and process your code.

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What does the fread function do in C?

The fread function in C is used to read a specified number of bytes of data from a file into a buffer. This lets you read data into a memory location for processing.

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Describe the fputc function in C.

The fputc function in C writes a single character to a file stream. You can use it to write data to a file sequentially, one character at a time.

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Study Notes

Preprocessor Directives

  • Instructions processed before compilation.
  • Begin with a #.
  • Used for including files, defining constants, and conditional compilation.

File Types

  • Text Files: Store data in a readable format (e.g., ".txt").
  • Binary Files: Store data in binary format. More efficient but not human-readable (e.g., images, executables).

File Handling Functions (fseek, ftell, rewind)

  • fseek(FILE *stream, long offset, int origin): Moves the file pointer.
    • offset: Number of bytes to move.
    • origin: Where to start the count (SEEK_SET, SEEK_CUR, SEEK_END).
  • ftell(FILE *stream): Returns the current position of the file pointer.
  • rewind(FILE *stream): Resets the file pointer to the beginning of the file.

Text vs. Binary Files

Feature Text Files Binary Files
Data Storage Human-readable Binary format
File Size Larger (due to encoding) Smaller
Access Slower (parsing required) Faster
Usage Logs, config files Images, executables

File Handling Example (ftell, fseek, rewind)

  • Demonstrates moving and resetting file pointers.
  • Shows how fseek moves 10 bytes from the start, ftell reports the new position.
  • rewind returns to the beginning.

Conditional Compilation (#ifdef, #ifndef, #undef)

  • Allows selective code compilation based on macro definitions.
  • #ifdef: Compiles code if the macro is defined.
  • #ifndef: Compiles code if the macro is not defined.
  • #undef: Removes the definition of a macro.
  • Example shows these directives in a program.

ftell Function

  • Returns the current position (byte offset from the beginning) of a file's pointer.
  • Used to keep track of where you are in a file for random access.

File Copying Program

  • Copies the contents of one file to another.
  • Uses fgetc and fputc for character-by-character copying, handling end-of-file.

fseek for Random Access

  • fseek enables access to any part of a file by positioning the file pointer.
  • Allows precise byte reading from various points in a file.

Preprocessor Directives (Detailed)

  • Executed before compilation.
  • #include: Includes other files into the source code.
  • #define: Defines macros (e.g., constants or text replacements).
  • #undef: Removes a macro definition.
  • #ifdef/#ifndef: Use conditional compilation to include/exclude code based on predefined macros.
  • #pragma: Provides compiler-specific instructions.

Printing Specific Records from a File

  • Reads a specified amount of records from the beginning of a given text file.
  • Demonstrates file reading to print a specified number of records from the start of a file.
  • Uses fgets to read lines from the file and prints them until the desired number of records is reached.

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