Introduction to C

C language features

• Provides lowlevel access to memory

• used in system programming

  • Operating systems: such as Linux
  • Microcontrollers: cars and planes
  • embedded systems: phones, portable electronics, ..

• used in derivation of C++, Objective C, C#

• C has enormous influence on other languages: Java, PHP, Python, . . .

• High-level but close to the hardware

• Fast: allows low-level programming

• compiles to native code

• C lacks: garbage collection, OOP, . . .

Installation

• Linux: included with most linux distributions
  • you can check it by entering this into the command line: gcc -v
• Mac OS: you need to install Xcode
• Windows: download and install MinGW, ensure that bin subdirectory is in PATH

Hello World!

#include <stdio.h>
int main(void)
{
  #"\n" is an escape character means "newline"
	printf("Hello World!\n");
  #0 indicates the program ends normally
	return 0;
}

• C standard library header files include function definitions, variable declarations.

#include <stdio.h>

• Other header files are math.h, stdlib.h, string.h, time.h.
• the main entry of the of C programs, returns integer (int) and has no parameters (void) followed by a curly bracket

Complie and run

• save the code in hello.c (.c is the extension used for c language programs)
• compile the program by entering to the command line

​ gcc hello.c

• this create an executable file a.out on Linux and Mac OS, and a.exe on Windows

• now you can run it by typing ./a.out (Linux MacOS) or a.exe (Windows)

• you can change the name of the output file with:

  gcc hello.c -o hello

C keywords and Identifiers

C keywords

Integer Types

Datatypes

• Integer Types
• in unsigned the most significant bit (MSB) will not be used as sign (+ or -)
• The header file limits.h has many useful constants to check the range of different datatypes: SCHAR_MIN, SCHAR_MAX, UCHAR_MAX, INT_MIN, INT_MAX, UINT_MAX, ...
• Floating-Point Types

• The header file float.h provides constants to check the range of float datatypes : FLT_MIN, FLT_MAX, ...
• the sizes and ranges may be different on you computer based on the platform you use (hardware and OS)