C Programming Fundamentals Quiz

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Questions and Answers

What command is used to compile a C program named 'teste.c'?

gcc -o teste teste.c (correct)

cc -execute teste.c

gcc -run teste.c

gcc compile teste.c

The option '-Wall' is used to disable warning messages during compilation.

False

What is the purpose of the '-O' option in gcc?

'-O' option is used to optimize the generated code.

The command to execute a compiled program is './______'

teste Signup and view all the answers

What does the command 'gcc -O3 -Wall -c prog.c' perform?

Only compiles 'prog.c' into an object file Signup and view all the answers

It is possible to combine the two compilation steps into one command using gcc.

True Signup and view all the answers

What file is generated after the first step of compiling 'prog.c'?

'prog.o' Signup and view all the answers

What does the function `wait()` return when called with no child processes?

-1 Signup and view all the answers

If a process calls `wait()` and all its child processes are still running, it will return immediately.

False Signup and view all the answers

What action must be taken if `execlp()` fails in the given code segment?

exit(1) Signup and view all the answers

In the code provided, the command list is defined as `char *cmd[] = {____};`

“who”, “ls”, “date” Signup and view all the answers

Match the following actions with their descriptions:

fork() = Creates a new process execlp() = Executes a program wait() = Suspends the calling process exit() = Terminates the process Signup and view all the answers

What happens in the parent process after calling `fork()`?

It continues executing independently of the child. Signup and view all the answers

Raw files are considered the least efficient and slowest method for storing and retrieving data.

False Signup and view all the answers

What will the program output after the child process completes?

child finished Signup and view all the answers

What does the function ftell return?

The current position of the cursor in the file Signup and view all the answers

The fseek function can only move the cursor forward in the file.

False Signup and view all the answers

What are the three constants that can be used for the origin parameter in fseek?

SEEK_SET, SEEK_CUR, SEEK_END Signup and view all the answers

The function __________ is equivalent to using fseek to move to position 0 in the file.

rewind Signup and view all the answers

Which of the following statements about the fseek function is correct?

It requires a file pointer and a displacement value. Signup and view all the answers

Match the following fseek parameters with their descriptions:

SEEK_SET = Indicates the beginning of the file SEEK_CUR = Indicates the current position of the cursor SEEK_END = Indicates the end of the file Signup and view all the answers

The displacement value in fseek can only be a positive number.

False Signup and view all the answers

What would the following line of code do? fseek(fichier, -4, SEEK_CUR)

Move the cursor 4 characters backward from the current position. Signup and view all the answers

What function is used to read a single character from a file?

fgetc Signup and view all the answers

The function fgets reads characters until it encounters EOF.

False Signup and view all the answers

What does the function ftell do in file handling?

It indicates the current position in the file. Signup and view all the answers

To reposition the cursor to the beginning of a file, you can use the function ______.

rewind Signup and view all the answers

Match the following file handling functions with their descriptions:

fgetc = Reads a single character fgets = Reads a string from a file fscanf = Reads formatted data from a file fseek = Moves the file cursor to a specific position Signup and view all the answers

What is the purpose of the fscanf function?

Read formatted data from a file Signup and view all the answers

The function fseek is used to determine the current position in a file.

False Signup and view all the answers

What does the function fscanf return when it successfully reads data from a file?

The number of input items successfully matched and assigned. Signup and view all the answers

In file handling, the function ______ is used to read a line of text into a string.

fgets Signup and view all the answers

Which function would you use to move the file cursor back to the beginning of the file?

rewind Signup and view all the answers

What is the role of the compiler in the development process?

Passes a source file to an object file Signup and view all the answers

The gcc is a type of text editor used in Linux.

False Signup and view all the answers

What file extension is used for programs written in C?

.c Signup and view all the answers

The _____ links object files from different modules with the libraries for the application.

linker Signup and view all the answers

Match the following components of system development with their functions:

Text Editor = Write and edit code Compiler = Convert source code to object code Linker = Combine object files into an executable Libraries = Provide reusable code modules Signup and view all the answers

Which one of the following is NOT a component in the system design?

Debugger Signup and view all the answers

The shell is an integral part of the system architecture in UNIX.

True Signup and view all the answers

Name one commonly used text editor in UNIX for writing C programs.

vi Signup and view all the answers

What does fork() do in a process management context?

Creates a new process Signup and view all the answers

If fork() returns -1, it indicates that a new process has been successfully created.

False Signup and view all the answers

What error code does a process receive when it needs to retry its duplicate request?

EAGAIN Signup and view all the answers

In the fork() example, the child process prints ‘CHILD %d’ while the parent process prints ‘______ %d’.

PARENT Signup and view all the answers

Match the programming construct with its description:

fork() = System call to create a new process errno = Holds the error codes for system calls getpid() = Returns the process ID of the calling process getppid() = Returns the parent process ID Signup and view all the answers

In what scenario would a process enter the do-while loop when calling fork()?

When the fork() call fails with errno set to EAGAIN. Signup and view all the answers

A parent process must wait for the child process to finish before it can continue executing.

False Signup and view all the answers

What is printed by the child process if the fork() returns 0?

Fils : PID=..., PPID=... Signup and view all the answers

In the second fork() example, the variable 'pid' is of type ______.

pid_t Signup and view all the answers

Which of the following is an incorrect way to use a for loop in the provided code?

for( i=0; I < 1000; i++ ) printf(‘CHILD %d ’, i); Signup and view all the answers

Study Notes

Introduction

This document contains notes on the presentation of programming systems, specifically focusing on processes.

Processes

A process is the memory image of a program currently running. It has a life cycle. It begins, runs, and then ends.
A program launched twice creates two distinct processes.
Every process is identified in memory by a unique number assigned by the operating system called the PID (Process ID).

Process Tree in a Unix System

The init process is the parent of all other processes in a Unix system.
init assigns the machine name, initializes the date and time, and ensures the system has been properly shut down.
It starts the "getty" process which displays "login" prompt on a terminal and waits for input.
It also launches the "inetd" process for network monitoring.
Processes ending in "d" are called "daemon" processes that are server processes which work in continuous loops to provide consistent service to clients.

Process States

Initial: newly created, in transition.
Active: the process is executing.
Waiting: the process is paused and relinquishes the CPU to another process.
Terminating: the process has finished execution.

Process Concepts

A processor executes one task at a time.
The process has various states, such as "Ready," "Running," "Blocked," and "Terminated." These states depict the behavior of the process.
Transitions happen between states on event occurrence. For instance, a process can transition to 'ready' from 'blocked' or 'terminated' on completion.

Process Creation

User processes are launched by a command interpreter (shell). They can also create further processes.
Processes need to interact among each other.
The creator process is termed a "Parent" process.
Processes created are referred to as "Children" processes.

Process Termination

Process termination can be done in 3 ways:
Normal Termination: Finishing its operations
Permitted Termination: By the parent process executing a suitable command
Abnormal Termination: By the system, such as exceeding execution time or insufficient memory.

Implementation

The operating system maintains a process table, or table of processes, to track individual processes.
Each entry contains information about the process, including its status, instruction address, stack pointer, open files, and the allocated memory.

Process Structure

An operating system process comprises various elements such as PID (Process ID), UID (User ID), GID (Group ID), open files, maximum file size, and priority.
The Terminal is the terminal from which a command was executed.

Priorities

Under Linux, processes have a priority of -20 to 19 to control execution order.
Higher values indicate lower priority.
The nice command is used to adjust process priority

Example: Structure of a Unix Process

Processes have unique IDs.
Processes have sets of open files and a current directory.
Processes have a certain priority, and execution time.

The ps command

Shows information about running processes.
Provides a list of processes linked to a specific terminal, along with CPU utilisation data.
Useful for viewing processes that aren't linked with terminals.

The kill command

Sends a signal to a process to perform an action.
Accepts a signal number.

Signals

A signal in an operating system is an asynchronous event that can interrupt the running of a program.
Signals can be generated by hardware events (e.g., a signal to inform a process that an interrupt has occurred), the operating system itself, another process, or an error condition within the process.
Example Signals: SIGINT, SIGQUIT, SIGKILL, etc.

Job Management

A job is a collection of one or more commands.
Commands, including programs, can be made into a job.
Launch jobs in the background via the '&' character.
The "jobs" command displays all running jobs.
Use the 'bg' command to resume the execution of a stopped job.
Use the 'fg' command to bring a job into the foreground.

Linux Management of Services

The "service" command manipulates machine services.
Shows status of all running services.
Useful for managing processes.

Concepts and Tools.

General information about Linux development.
Information for developers on interaction between application and the machine.
Information about system calls.

Development in Linux

There are three basic steps in Linux development:
- Editing the source code.
- Compiling the source code into an executable file.
- Linking the object files with the required libraries into a single executable file.

Compiling and Linking

The compiler/linker (gcc) converts source code into machine language.
Different options are used during compilation, like ‘-g’ for debugging and ‘-Wall’ to display warnings.

Execution

An example of how to run C code.
How to compile, execute programs in Linux.

Example

Illustrative examples for various program execution scenarios.

Compilation in C

Explains the compilation process in C programs using gcc.

The Makefile

Managing multiple source files and dependencies within a C project.
Using a makefile to automate compilation for large projects.
Ways to write the different rules to automate compilation.
Ways to define rules to automate compilation.
Ways to define variables within a makefile for reuse.
A guide on how to write, read and correctly interpret a makefile.

Parameters to "main()"

Explanation of parameters in the main() function in a C program, including argc, argv, and envp.
Explains what each parameter represents and how they are used within the program.
Gives some example implementations in order to better understand their usage.

The PATH Variable

The value of PATH is a set of paths.
The executables are searched at all the paths defined within the PATH value.

Access to Environment

How to access environment variables in code.
Example usage and retrieval of values.

System Calls C

Methods for creating and manipulating processes in C.
Explanation of the system calls and their use in controlling process behavior.
- Description of the 'fork' system call.

The `fork` System Call

Usage: Creation of child processes, and how processes can communicate with each other after using fork().

Process Presentation

Explains how processes are presented.
Clarifies the parent-child relationship between two processes, and illustrates how the system deals with the parent process after the creation of a child process.

The `wait` System Call

How to wait for a child process's status after the fork system call is used.
This call is used to ensure the parent process stops till the child process ends, therefore allowing processes to complete in sequence.

Displaying the Date with the Child Process

Demonstrates an example of using the fork and execv system calls to run a command, and capture its output to display within the current application.

Implementing Files

Describes the various methods for interacting with files.
Explains how raw file manipulation can differ from the standard input and output operations.

File Descriptors

Discusses the concept of file descriptors for identifying files in a C program
Explains the importance of understanding file descriptors in performing file operations.

`stat` Structure

How to access file details using stat.
Describes the contents of the struct stat to indicate file information like permissions, creation, modification, and access times.

File Writing

Explanation of writing operations on files in C using the write system call.

File Reading

Explanation of reading operations on files in C using the read system call.

File Management

Various methods for managing and manipulating files in C, including creating, writing, reading, closing, and renaming files.

File Buffering

Explains file buffering and its relationship with file I/O operations.

File Operations

A summary of file operations and the necessary headers.

Standard POSIX

Summary of the POSIX standard and its relevance to file operations.

Named Pipes

Explanation of named pipes for inter-process communication.
Showing how named pipes can persist across process terminations.

Signal Handling

Introduction to signals and how they can be handled in C programs to make applications more robust.
Illustrates how signal handling can be managed in processes to handle errors, or to perform some task when an error is encountered.

Signals : CTRL-C & CTRL-Z

Illustrates how the CTRL+C and CTRL+Z commands can be used to interrupt a program.

Signal Handling

Explains different ways to handle signals.
Explanation of how to handle signals including the use of signal(), pause(), and alarm().
Explains the structure, role, handling of signals.
- Includes code examples, to help to understand the different signal handling.

Signal Interface

Explains the interface for managing signals in C programs.

Signal Values in Unix

Explains the different signal values in Unix-like systems (Linux).

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Description

Test your knowledge on C programming concepts, including compilation commands and process handling. This quiz covers essential gcc options, file generation, and process management functions like wait and fork. Perfect for beginners looking to solidify their understanding of C programming basics.

C Programming Fundamentals Quiz

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Questions and Answers

What command is used to compile a C program named 'teste.c'?

The option '-Wall' is used to disable warning messages during compilation.

What is the purpose of the '-O' option in gcc?

The command to execute a compiled program is './______'

What does the command 'gcc -O3 -Wall -c prog.c' perform?

It is possible to combine the two compilation steps into one command using gcc.

What file is generated after the first step of compiling 'prog.c'?

What does the function wait() return when called with no child processes?

If a process calls wait() and all its child processes are still running, it will return immediately.

What action must be taken if execlp() fails in the given code segment?

In the code provided, the command list is defined as char *cmd[] = {____};

Match the following actions with their descriptions:

What happens in the parent process after calling fork()?

Raw files are considered the least efficient and slowest method for storing and retrieving data.

What will the program output after the child process completes?

What does the function ftell return?

The fseek function can only move the cursor forward in the file.

What are the three constants that can be used for the origin parameter in fseek?

The function __________ is equivalent to using fseek to move to position 0 in the file.

Which of the following statements about the fseek function is correct?

Match the following fseek parameters with their descriptions:

The displacement value in fseek can only be a positive number.

What would the following line of code do? fseek(fichier, -4, SEEK_CUR)

What function is used to read a single character from a file?

The function fgets reads characters until it encounters EOF.

What does the function ftell do in file handling?

To reposition the cursor to the beginning of a file, you can use the function ______.

Match the following file handling functions with their descriptions:

What is the purpose of the fscanf function?

The function fseek is used to determine the current position in a file.

What does the function fscanf return when it successfully reads data from a file?

In file handling, the function ______ is used to read a line of text into a string.

Which function would you use to move the file cursor back to the beginning of the file?

What is the role of the compiler in the development process?

The gcc is a type of text editor used in Linux.

What file extension is used for programs written in C?

The _____ links object files from different modules with the libraries for the application.

Match the following components of system development with their functions:

Which one of the following is NOT a component in the system design?

The shell is an integral part of the system architecture in UNIX.

Name one commonly used text editor in UNIX for writing C programs.

What does fork() do in a process management context?

If fork() returns -1, it indicates that a new process has been successfully created.

What error code does a process receive when it needs to retry its duplicate request?

In the fork() example, the child process prints ‘CHILD %d’ while the parent process prints ‘______ %d’.

Match the programming construct with its description:

In what scenario would a process enter the do-while loop when calling fork()?

A parent process must wait for the child process to finish before it can continue executing.

What is printed by the child process if the fork() returns 0?

In the second fork() example, the variable 'pid' is of type ______.

Which of the following is an incorrect way to use a for loop in the provided code?

Study Notes

Introduction

Processes

Process Tree in a Unix System

Process States

Process Concepts

Process Creation

Process Termination

Implementation

Process Structure

Priorities

Example: Structure of a Unix Process

The ps command

The kill command

Signals

Job Management

Linux Management of Services

Concepts and Tools.

Development in Linux

Compiling and Linking

Execution

Example

Compilation in C

The Makefile

Parameters to "main()"

What does the function `wait()` return when called with no child processes?

If a process calls `wait()` and all its child processes are still running, it will return immediately.

What action must be taken if `execlp()` fails in the given code segment?

In the code provided, the command list is defined as `char *cmd[] = {____};`

What happens in the parent process after calling `fork()`?

The `fork` System Call

The `wait` System Call

`stat` Structure