Systems Programming and C Fundamentals

This set covers systems programming definitions, software categories, OS architecture specifically Linux, system calls, the differences between C and C++, bitwise operators, and memory manipulation functions.

System

A collection of various components.

Programming

The activity of designing and implementing programs.

Systems Programming

The activity of designing and implementing system programs.

System Programs

Programs required for the effective execution of general user programs on a computer system.

Utilities

Small programs or tools designed to perform specific tasks that help manage, maintain, or support system functionality.

Application Software

A program or set of programs used to solve a problem using the computer as an instrument, providing services to the user like word processors or web browsers.

System Software

Software that supports the operation of the computer, interfacing between hardware and application software, including compilers, loaders, and operating systems.

Operating System (OS)

A special program that resides between the computer hardware and application software.

Linux

A multiuser, multitasking, free and open source operating system with a Unix-like feel.

Linux Distributions

Packages consisting of the Linux kernel, basic software/utilities, and a package manager; examples include Debian, Fedora, Gentoo, and Kali.

Kernel

The central part of the OS that interfaces directly with the hardware.

Shell

The user interface for command execution in a Linux OS architecture.

System Calls

Generally available as assembly-language instructions, these provide the API interaction with system resources and transition the system from user mode to kernel mode.

GNU C Library (glibc)

A library that facilitates system calls by providing wrappers, support for threading, and basic application services.

User Mode

A CPU mode where certain instructions, such as modifying page tables, are prohibited to prevent abuse.

Kernel Mode

A privileged CPU mode where the OS code takes control, updates privileges, and performs requested functions.

Context-switch

The expensive process where the hardware saves its state and the OS code takes control of the CPU during a system call.

errno

A variable used to store an error number when a system call error occurs.

perror()

A function called to display an error message when a system call fails.

Procedural Programming

The programming paradigm followed by C where importance is given to the sequence of steps and a top-down approach.

Function Overloading

A feature supported by C++ using polymorphism that allows multiple functions with the same name, which is absent in C.

NAMESPACE

A feature in C++ used to avoid name collisions that is not present in C.

Reference Variables

A feature in C++ that allows two variable names to point to the same memory location, which is not allowed in C.

Bitwise Operators

Operators that perform bit-by-bit operations on integral types, providing the power of a low-level language for memory manipulation.

Mask

A value used in conjunction with bitwise operators to set bits on or off or to determine if a bit is currently on or off.

memcpy

$void *memcpy (void *dest, const void *src, size_t n);$ - Copies a block of $n$ bytes from src to dest and returns a pointer to dest.

memset

$void *memset (void *s, int c, size_t n);$ - Sets $n$ bytes of s to the byte value c.

memcmp

$int memcmp (const void *s1, const void *s2, size_t n);$ - Compares the first $n$ bytes of two arrays; the comparison is case sensitive.