Basics of C
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Transcript of Basics of C
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Basics of C
Session 1
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Elementary Programming with C/Session 1/ 2 of 26
Objectives Differentiate between Command, Program
and Software Explain the beginning of C Explain when and why is C used Discuss the C program structure Discuss algorithms Draw flowcharts List the symbols used in flowcharts
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Elementary Programming with C/Session 1/ 3 of 26
Software, Program and Command
Software
Program 2
Program 1
Comman
ds
Comman
ds
Comman
ds
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Elementary Programming with C/Session 1/ 4 of 26
The Beginning of C
C – Dennis Ritchie
B – Ken Thompson
BPCL – Martin Richards
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Elementary Programming with C/Session 1/ 5 of 26
Application Areas Of C C was initially used for systems programming
A system program forms a portion of the operating system of the computer or its support utilities Operating Systems, Interpreters, Editors, Assembly programs are usually called system programs The UNIX operating system was developed using C There are C compilers available for almost all types of PC’s
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Elementary Programming with C/Session 1/ 6 of 26
Middle Level LanguageHigh Level Language
Assembly Language
C
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Elementary Programming with C/Session 1/ 7 of 26
Structured Language
C allows compartmentalization of code and data It refers to the ability to section off and hide all information and instructions, necessary to perform a specific task, from the rest of the program
Code can be compartmentalized in C by using
functions or code blocks.
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Elementary Programming with C/Session 1/ 8 of 26
About C
C has 32 keywords
These keywords combined with a formal syntax
form a C programming language
Rules to be followed for all programs written in C: All keywords are lowercased
C is case sensitive, do while is different from DO WHILE Keywords cannot be used as a variable or function name
main(){/* This is a sample Program*/ int i,j; i=100; j=200; : }
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Elementary Programming with C/Session 1/ 9 of 26
The C Program Structure-1
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Elementary Programming with C/Session 1/ 10 of 26
The C Program Structure-2
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Elementary Programming with C/Session 1/ 11 of 26
The C Program Structure-3
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Elementary Programming with C/Session 1/ 12 of 26
The C Program Structure-4
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Elementary Programming with C/Session 1/ 13 of 26
The C Library All C compilers come with a standard library of functions
A function written by a programmer can be placed in the library and used when required
Some compilers allow functions to be added in the standard library
Some compilers require a separate library to be created
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Elementary Programming with C/Session 1/ 14 of 26
Compiling & Running A Program
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Elementary Programming with C/Session 1/ 15 of 26
The Programming Approach to Solving
ProblemsClassroom
Leaving the classroom
Head towards the staircase
Go to thebasement
Head for the cafeteria
Cafeteria
Algorithm is a set of steps that are performed to solve a problem. The example below describes an algorithm
These are the steps followed when a student wants to go to the cafeteria from the classroom
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Elementary Programming with C/Session 1/ 16 of 26
Solving a Problem
In order to solve a problem
Understand the problem clearly
Gather the relevant information
Process the information
Arrive at the solution
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Elementary Programming with C/Session 1/ 17 of 26
PseudocodeIt is not actual code. A method of algorithm - writing which uses a standard set of words which makes it resemble code
Each pseudocode starts with a BEGIN
To show some value , the word DISPLAY is usedThe pseudocode finishes with an END
BEGINDISPLAY ‘Hello World !’END
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Elementary Programming with C/Session 1/ 18 of 26
FlowchartsIt is a graphical representation of an
algorithm
START
DISPLAY ‘Hello World !’
STOP
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Elementary Programming with C/Session 1/ 19 of 26
The Flowchart Symbol
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Elementary Programming with C/Session 1/ 20 of 26
Flowchart to add two numbers
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Elementary Programming with C/Session 1/ 21 of 26
The IF Construct
BEGININPUT numr = num MOD 2IF r=0Display “Number is
even”END IFEND
S TART
INP UT num
r = num M OD 2
r = 0
DIS P LAY "Num ber is E ven"
S TOP
Yes
No
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Elementary Programming with C/Session 1/ 22 of 26
The IF-ELSE Construct
BEGININPUT numr=num MOD 2IF r=0 DISPLAY “Even Number”ELSE DISPLAY “Odd Number”END IFEND
S TA RT
INP UT num
r = num M O D 2
r = 0
DIS P LAY "Num ber is E ven"
S TOP
DIS PLA Y " Num ber is O dd"
Yes No
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Elementary Programming with C/Session 1/ 23 of 26
Multiple criteria using AND/OR
BEGININPUT yearsWithUsINPUT bizDoneIF yearsWithUs >= 10 AND bizDone >=5000000
DISPLAY “Classified as an MVS”ELSE
DISPLAY “A little more effort required!”END IFEND
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Elementary Programming with C/Session 1/ 24 of 26
Nested IFs-1BEGININPUT yearsWithUsINPUT bizDoneIF yearsWithUs >= 10 IF bizDone >=5000000
DISPLAY “Classified as an MVS” ELSE
DISPLAY “A little more effort required!”END IFELSE
DISPLAY “A little more effort required!”END IFEND
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Elementary Programming with C/Session 1/ 25 of 26
Nested IFs-2
INPUT YearsWithUs
START
INPUT bizDone
YearsWithUs >= 10
bizDone > 5000000
DISPLAY “A Little more effort required”
STOP
NOYES
NO
YES
DISPLAY “A Little more effort required”
DISPLAY “Classified as an MVS”
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Elementary Programming with C/Session 1/ 26 of 26
Loops
BEGINcnt=0WHILE (cnt < 1000)DO
DISPLAY “Scooby”cnt=cnt+1
END DOEND
S TA RT
cnt=0
cnt < 1000
DIS PLA Y " Sc ooby "
cnt=c nt+1
S TOP
Yes
No