1. Week 1 – Introduction to Computer and Algorithm (Part 2)‏
UniMAP Sem I-13/14
EKT120: Computer Programming

2. EKT120: Computer Programming
Outline
Pseudo code & flowchart
Sample programming question
Sample C program
Identifiers and reserved words
Program comments
Pre-processor directives
Data types and type declarations
Operators
Formatted input and output
Program debugging
UniMAP Sem I-13/14
EKT120: Computer Programming

3. Sample Programming Question
Write a program that calculates area of triangle. Your program should read the base length and the height length from user. Given the formula to calculate the area of triangle: 0.5 x (base) x (height).
Steps:
Analyze the problem
Use algorithm
Convert to actual codes
UniMAP Sem I-13/14
EKT120: Computer Programming

4. Recall..Pseudo code and Flowchart
Try develop the pseudo code and flowchart for the problem given in the previous slide.
UniMAP Sem I-13/14
EKT120: Computer Programming

5. Sample C Program Comments Preprocessor directives begin
/*Program name : program1.c
Programmer : Yasmin
This program calculates the area of triangle*/
#include <stdio.h>
int main(void)‏ {
double dBase, dHeight, dArea;
printf(“Enter base length : “);
scanf(“%f”, &dBase);
printf(“Enter height length : “);
scanf(“%f”, &dHeight);
dArea=0.5 * dBase * dHeight;
printf(“\nArea of the triangle is : %5.2f\n”, dArea);
return 0; }
Comments
Preprocessor directives
begin
The term void indicates we receive nothing from OS and return an integer to OS
Variables
declaration
body
return 0 (int) to OS
end
UniMAP Sem I-13/14
EKT120: Computer Programming

6. Variables & Reserved Words
Identifiers/Variables
labels for program elements
case sensitive
can consist of capital letters[A..Z], small letters[a..z], digit[0..9], and underscore character _
First character MUST be a letter or an underscore
No blanks
Reserved words cannot be variables/identifiers
Reserved words
already assigned to a pre-defined meaning
e.g.: delete, int, main, include, double, for, if, etc.
UniMAP Sem I-13/14
EKT120: Computer Programming

7. Variables & Reserved Words
An identifier for the data in the program
Hold the data in your program
Is a location (or set of locations) in memory where a value can be stored
A quantity that can change during program execution
UniMAP Sem I-13/14
EKT120: Computer Programming

8. EKT120: Computer Programming
Constants
A constant is a named or unnamed value, which does not change during the program execution.
Example:
const double dPi= ;
const int iDegrees=360;
const char cQuit=‘q’;
Unnamed constant are often called literals
Eg: and 360
UniMAP Sem I-13/14
EKT120: Computer Programming

9. EKT120: Computer Programming
Program Comments
Starts with /* and terminates with */ OR
Character // starts a line comment, if several lines, each line must begin with //
Comments cannot be nested /* /* */*/
UniMAP Sem I-13/14
EKT120: Computer Programming

10. Preprocessor Directives
An instruction to pre-processor
Standard library header: <stdio.h>,<math.h>
E.g. #include <stdio.h>
for std input/output
#include <stdlib.h>
Conversion number-text vise-versa, memory allocation, random numbers
#include <string.h>
string processing
UniMAP Sem I-13/14
EKT120: Computer Programming

11. EKT120: Computer Programming
Data Types
Data types determine the following:
Type of data stored
Number of bytes it occupies in memory
Range of data
Operations that can be performed on the data
Modifiers alter the meaning of the base type to more precisely fit a specific need
C supports the following modifiers along with data types:
short, long, signed, unsigned
UniMAP Sem I-13/14
EKT120: Computer Programming

12. Data Types & Memory Allocation
Bits
Bytes
Range
Char or Signed Char 8 1
-128 to +127
Unsigned Char
0 to +255
Int or Signed int 32 4
-2,147,483,648 to +2,147,483,647
Unsigned int
0 to +4,294,967,295
Short int or Signed short int 16 2
-32,768 to + +32,767
Unsigned short int
0 to +65,535
Long int or signed long int
Unsigned long int
Float
3.4 e-38 to 3.4 e+38
Double 64
1.7e-308 to 1.7e+308
Long Double
UniMAP Sem I-13/14
EKT120: Computer Programming

13. Variables Naming Conventions
Variable names should use Hungarian notation
Start with an appropriate prefix that indicates the data type
After the prefix, the name of variable should have ore or more words
The first letter of each word should be in upper case
The rest of the letter should be in lower case.
The name of variable should clearly convey the purpose of the variable
UniMAP Sem I-13/14
EKT120: Computer Programming

14. Naming Variables According to Standards
Prefix
Data Type
Example i
int and unsigned int
iTotalScore f
float
fAverageScore d
double
dHeight l
long and unsigned long
lFactorial c
signed char and unsigned char
cProductCode ai
Array of integer
aiStudentId af
Array of float
afWeight ad
Array of double
adAmount al
Array of long integer
alSample ac
Array of characters
acMaterial
UniMAP Sem I-13/14
EKT120: Computer Programming

15. Data Types Declaration
float fIncome;
float fNet_income;
double dBase, dHeight, dArea;
int iIndex =0, iCount =0;
char cCh=‘a’, cCh2;
const float fEpf = 0.1, fTax = 0.05;
float income, net_income;
Declare and initialize
Named constant declared and initialized
UniMAP Sem I-13/14
EKT120: Computer Programming

16. EKT120: Computer Programming
Types of Operators
Types of operators are:
Arithmetic operators
(+ , - , * , / , %)‏
Relational operators
(> , < , == , >= , <=, !=)‏
Logical operators (&& , ||)‏
Compound assignment operators
(+=, -=, *=, /=, %=)‏
Binary operators: needs two operands
Unary operators: single operand
Bitwise operators: executes on bit level
UniMAP Sem I-13/14
EKT120: Computer Programming

17. EKT120: Computer Programming
Arithmetic Operators
Used to execute mathematical equations
The result is usually assigned to a data storage (instance/variable) using assignment operator ( = )‏
E.g.
sum = marks1 + marks2;
UniMAP Sem I-13/14
EKT120: Computer Programming

18. EKT120: Computer Programming
Arithmetic Operators
r % s
r mod s %
Remainder
(Modulus)‏
x / y /
Division
b * m bm *
Multipication
p - c
p – c -
Subtraction
f + 7 +
Addition
C Expression
Algebraic Expression
Arithmetic Operator
C Operation
UniMAP Sem I-13/14
EKT120: Computer Programming

19. Exercise on Arithmetic Operators
Given x = 20, y = 3
z = x % y
= 20 % 3
= 2 (remainder)‏
UniMAP Sem I-13/14
EKT120: Computer Programming

20. Relational and Logical Operators
Previously, relational operator:
>, < >=, <=, == , !=
Previously, logical operator:
&&, ||
Used to control the flow of a program
Usually used as conditions in loops and branches
UniMAP Sem I-13/14
EKT120: Computer Programming

21. More on relational operators
Relational operators use mathematical comparison (operation) on two data, but give logical output
e.g.1 let say b = 8, if (b > 10)‏
e.g.2 while (b != 10)‏
e.g.3 if (mark == 60) print (“Pass”);
Reminder:
DO NOT confuse == (relational operator)
with = (assignment operator)‏
UniMAP Sem I-13/14
EKT120: Computer Programming

22. More on logical operators
Logical operators are manipulation of logic. For example:
i. b=8, c=10,
if ((b > 10) && (c<10))‏
ii. while ((b==8) || (c > 10))‏
iii. if ((kod == 1) && (salary > 2213))‏
UniMAP Sem I-13/14
EKT120: Computer Programming

23. Truth Table for && (logical AND) Operator
true
false
exp1 && exp2
exp2
exp1
UniMAP Sem I-13/14
EKT120: Computer Programming

24. Truth Table for || (logical OR) Operator
true
false
exp1 || exp2
exp2
exp1
UniMAP Sem I-13/14
EKT120: Computer Programming

25. Compound Assignment Operators
To calculate value from expression and store it in variable, we use assignment operator (=)‏
Compound assignment operator combines binary operator with assignment operator
E.g. val +=one; is equivalent to val = val + one;
E.g. count = count -1; is equivalent to
count -=1;
count--;
--count;
UniMAP Sem I-13/14
EKT120: Computer Programming

26. EKT120: Computer Programming
Unary Operators
Obviously operating on ONE operand
Commonly used unary operators
Increment/decrement { ++ , -- }
Arithmetic Negation { - }
Logical Negation { ! }
Usually using prefix notation
Increment/decrement can be both a prefix and postfix
UniMAP Sem I-13/14
EKT120: Computer Programming

27. Comparison of Prefix and Postfix Increments
UniMAP Sem I-13/14
EKT120: Computer Programming

28. Unary Operators (Example)‏
Increment/decrement { ++ , -- }
prefix:value incr/decr before used in expression
postfix:value incr/decr after used in expression
val=5;
printf (“%d”, ++val);
Output: 6
val=5;
printf (“%d”, --val);
Output: 4
val=5;
printf (“%d”, val++);
Output: 5
val=5;
printf (“%d”, val--);
Output: 5
UniMAP Sem I-13/14
EKT120: Computer Programming

29. EKT120: Computer Programming
Operator Precedence
last =
seventh ||
sixth
&&
fifth
== !=
fourth
< <= >= >
third
+ - (binary operators)
second
* / %
first
! (unary operators)
Precedence
Operators
UniMAP Sem I-13/14
EKT120: Computer Programming

30. Formatted Output with “printf”
#include <stdio.h>
void main (void) {
int iMonth;
float fExpense, fIncome;
iMonth = 12;
fExpense = 111.1;
fIncome = ;
printf (“Month=%2d, Expense=$%9.2f\n”,iMonth,fExpense); }
Declaring variable (fMonth) to be int integer
Declaring variables (fExpense and fIncome) to be real
Assignment statements store numerical values in the memory cells for the declared variables
‘,’ separates string literal from variable names
Correspondence between variable names and %...in string literal
UniMAP Sem I-13/14
EKT120: Computer Programming

31. Formatted Output with printf-cont
printf (“Month= %2d, Expense=$ %9.2f \n” ,iMonth, fExpense);
%2d refer to variable iMonth value.
%9.2f refer to variable fExpense value.
The output of printf function will be displayed as
UniMAP Sem I-13/14
EKT120: Computer Programming

32. Formatted input with scanf
UniMAP Sem I-13/14
EKT120: Computer Programming

33. Formatted input with scanf-cont
UniMAP Sem I-13/14
EKT120: Computer Programming

34. EKT120: Computer Programming
Program debugging
Syntax error
Mistakes caused by violating “grammar” of C
C compiler can easily diagnose during compilation
Run-time error
Called semantic error or smart error
Violation of rules during program execution
C compiler cannot recognize during compilation
Logic error
Most difficult error to recognize and correct
Program compiled and executed successfully but answer wrong
UniMAP Sem I-13/14
EKT120: Computer Programming

35. Program debugging-syntax error snapshot
UniMAP Sem I-13/14
EKT120: Computer Programming

36. Program debugging-run time error snapshot
UniMAP Sem I-13/14
EKT120: Computer Programming

37. Program debugging-logic error snapshot
UniMAP Sem I-13/14
EKT120: Computer Programming

38. EKT120: Computer Programming
End Week 1 – Session 2
Q & A!
UniMAP Sem I-13/14
EKT120: Computer Programming