Overview in C , some basic stuff, Lecture notes of C programming

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EEE 11: Lecture 2

C Overview

Meet 'P'

● Can move up, down, left and right

● Can move along the following items

− Road

− Bridge

● Understands only the following:

− “U” - move up one step

− “D” - move down one step

− “R” - move right one step

− “L” - move left one step

Programming Language

● Set of instructions or commands that the machine

can understand

− Allows you to control the computer

● Has is own grammar called Syntax

● Example:

− Apple red is a fruit

− Form a circle and make it straight

The C Programming Language

● Medium-level programming language (higher level than

assembly language)

● Developed in the 1970's by Ken Thompson and Dennis Ritchie

− Ritchie is one of the authors of “The C Programming Language”

Sample 02-

Hello there!

Displays Hello there

#include <stdio.h>

int main (void)

printf(“Hello there!\n”); /* Display text */

return 0;

Sample code 02-01: Simple C code

Preprocessor directive

Comments

Statements

Main function

Sample 02-

a = 10

Display a

Variable Declarations

● Define the name and the kind of information stored

● REQUIRED BEFORE USE

● Variable

− A name associated with a data whose value can change during program execution

● Data Type

− A name or label for a set of values and operations that can be performed on those values e.g. An integer can be added, subtracted, multiplied, etc

Variable Declaration Formats

● Syntax

<variable_list>; *variable_list are comma-separated names

● Examples

/* Single declaration */ int count;

/* multiple declarations */ float miles, kms; int number1,

number2, /* can span several lines */

number3; /* not recommended */

Identifier Rules

● Must consist only of

− letters [A,..,Z,a,...,z] − Digits [0,..,9] − Underscores _

● Cannot begin with a digit

− Valid identifiers: _abc, letter1, letter2, inches, Hello, VARiable − Invalid identifiers: 1_a, .name, (number

● Case-sensitive

− inches and INCHES are not the same

● Some compilers consider only the first 31 characters

Review

Classify the words as

(a) valid identifiers (b) invalid identifier

9teen double sqrt

#insert return this_is_an_example

printf xyz123 void

G Sue's

Reserved Identifiers

● Words that have special meaning in C

− Also known as Keywords

● Standard Identifiers

− Names that are not reserved but are used by the C standard libraries

Standard Identifiers

● Names of functions defined in the standard libraries

● Can be redefined and used for other purposes

− NOT RECOMMENDED!

stdio.h math.h stdlib.h printf sqrt atof scanf exp atoi getc sin strtod

Use consistent naming style

(see our resources page for sample)

● Constants are all UPPERCASE

● User-defined identifiers are in lowercase

− No mixed cases (eg maxHeight)

● Assign meaningful identifier names

− Keep it short (e.g. SMS lingo) − Single characters are OK for short codes

● Do not choose names that are similar to each other

− LARGE and large − xcoord and x_coord

● BE CONSISTENT!