UniMAP Sem II-10/11EKT120: Computer Programming1 Week 1 – Introduction to Computer and Algorithm (Part 2)‏

EKT120: Computer Programming2 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 II-10/11

EKT120: Computer Programming3 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 II-10/11

Recall..Pseudo code and Flowchart Try develop the pseudo code and flowchart for the problem given in the previous slide. EKT120: Computer Programming4 UniMAP Sem II-10/11

EKT120: Computer Programming5 Sample C Program /*Program name : program1.c Programmer : Yasmin This program calculates the area of triangle*/ #include 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; } The term void indicates we receive nothing from OS and return an integer to OS Variables declaration begin end return 0 (int) to OS body Comments Preprocessor directives UniMAP Sem II-10/11

EKT120: Computer Programming6 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 II-10/11

EKT120: Computer Programming7 UniMAP Sem II-10/11  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 Variables & Reserved Words

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 EKT120: Computer Programming8 UniMAP Sem II-10/11

EKT120: Computer Programming9 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 II-10/11

EKT120: Computer Programming10 Preprocessor Directives An instruction to pre-processor Standard library header:, E.g. #include for std input/output #include Conversion number-text vise-versa, memory allocation, random numbers #include string processing UniMAP Sem II-10/11

EKT120: Computer Programming11 Data Types UniMAP Sem II-10/11  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

EKT120: Computer Programming12 Data Types & Memory Allocation UniMAP Sem II-10/11 TypeBitsBytesRange Char or Signed Char to +127 Unsigned Char810 to +255 Int or Signed int324-2,147,483,648 to +2,147,483,647 Unsigned int3240 to +4,294,967,295 Short int or Signed short int162-32,768 to + +32,767 Unsigned short int1620 to +65,535 Long int or signed long int324-2,147,483,648 to +2,147,483,647 Unsigned long int3240 to +4,294,967,295 Float e-38 to 3.4 e+38 Double6481.7e-308 to 1.7e+308 Long Double6481.7e-308 to 1.7e+308

EKT120: Computer Programming13 Variables Naming Conventions UniMAP Sem II-10/11  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

EKT120: Computer Programming14 Naming Variables According to Standards UniMAP Sem II-10/11 PrefixData TypeExample iint and unsigned intiTotalScore ffloatfAverageScore ddoubledHeight llong and unsigned longlFactorial csigned char and unsigned charcProductCode aiArray of integeraiStudentId afArray of floatafWeight adArray of doubleadAmount alArray of long integeralSample acArray of charactersacMaterial

EKT120: Computer Programming15 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 II-10/11

EKT120: Computer Programming16 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 II-10/11

EKT120: Computer Programming17 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 II-10/11

EKT120: Computer Programming18 Arithmetic Operators r % s r mod s % Remainder (Modulus)‏ x / y / Division b * m bm * Multipication p - c p – c - Subtraction f Addition C ExpressionAlgebraic Expression Arithmetic Operator C Operation UniMAP Sem II-10/11

EKT120: Computer Programming19 Exercise on Arithmetic Operators Given x = 20, y = 3 z = x % y = 20 % 3 = 2 (remainder)‏ UniMAP Sem II-10/11

EKT120: Computer Programming20 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 II-10/11

EKT120: Computer Programming21 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 II-10/11

EKT120: Computer Programming22 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 II-10/11

EKT120: Computer Programming23 Truth Table for && (logical AND) Operator true false true falsetruefalse exp1 && exp2exp2exp1 UniMAP Sem II-10/11

EKT120: Computer Programming24 Truth Table for || (logical OR) Operator true falsetrue false exp1 || exp2exp2exp1 UniMAP Sem II-10/11

EKT120: Computer Programming25 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 II-10/11

EKT120: Computer Programming26 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 II-10/11

Comparison of Prefix and Postfix Increments EKT120: Computer Programming UniMAP Sem II-10/11

EKT120: Computer Programming28 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 II-10/11

EKT120: Computer Programming29 Operator Precedence last= seventh|| sixth&& fifth== != fourth = > third+ - (binary operators) second* / % first! + - (unary operators) PrecedenceOperators UniMAP Sem II-10/11

Formatted Output with “printf” #include void main (void) { int iMonth; float fExpense, fIncome; iMonth = 12; fExpense = 111.1; fIncome = ; printf (“Month=%2d, Expense=$%9.2f\n”,iMonth,fExpense); } EKT120: Computer Programming30 Declaring variable (fMonth) to be integer Declaring variables (fExpense and fIncome) to be real Assignment statements store numerical values in the memory cells for the declared variables Correspondence between variable names and %...in string literal ‘, ’ separates string literal from variable names UniMAP Sem II-10/11

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 II-09/10EKT120: Computer Programming31

EKT120: Computer Programming32 Formatted input with scanf UniMAP Sem II-10/11

EKT120: Computer Programming33 Formatted input with scanf- cont UniMAP Sem II-10/11

EKT120: Computer Programming34 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 II-10/11

EKT120: Computer Programming35 Program debugging-syntax error snapshot UniMAP Sem II-10/11

EKT120: Computer Programming36 Program debugging-run time error snapshot UniMAP Sem II-10/11

EKT120: Computer Programming37 Program debugging-logic error snapshot UniMAP Sem II-10/11

EKT120: Computer Programming38 End Week 1 – Session 2 Q & A! UniMAP Sem II-10/11