Chapter 1 Getting Started Structured Programming 1

Transcription

1 Chapter 1 Getting Started Structured Programming 1

2 Outline Introduction to Programming Algorithm Programming Style The printf( ) Function Common Programming Errors Introduction to Modularity Top-Down Program Development Chapter Summary Structured Programming 2

3 Introduction to Programming Computer program is a sequence of instructions used to operate a computer to produce a specific result Programming language is a set of instructions used to construct a program Structured Programming 3

4 IPO: Input, Process, Output Main Hardware Component Input Devices Central Processing Unit Main Memory Output Devices Secondary Storage Devices Structured Programming 4

5 Set of Instructions & Library Functions Structured Programming 5

6 FORmula TRANslation (FORTRAN) Structured Programming 6

7 COmmon Business Oriented Language (COBOL) Current trend Programming Languages that can manipulate database: VB JAVA etc Structured Programming 7

8 Algorithm is a step-by-step sequence of instructions that describes how to perform a computation a solution to a computer programming problem Example if we want to calculate the sum of whole numbers from 1 through Structured Programming 8

9 Summing the numbers 1 through Structured Programming 9

10 Summing the numbers 1 through 100 (cont.) Structured Programming 10

11 Algorithms for summing the numbers 1 through 100 Set n equal to 100 Set a equal to 1 Set b equal to 100 Calculate sum = n(a+b)/2 Formula Print the sum Structured Programming 11

12 Pseudocode & Flowchart Pseudocode is English phrases used to describe the algorithm (the processing steps) English-like steps that describes the solution Flowchart provides a pictorial representation of the algorithm using the symbols picture with specific blocks detailing out the logical flow of the solution Structured Programming 12

13 From Algorithms to Programs Coding Structured Programming 13

14 From Algorithms to Programs C Source Code #include <stdio.h> #include <conio.h> int main() { int n, remainder; clrscr(); printf("input n : "); scanf("%d", &n); remainder = n % 2; if (remainder == 0) printf ("n is even number\n"); else printf ("n is odd number\n"); getch(); return 0; } Problem Statement Read a number from the keyboard. Check and output if a given number N is ODD or EVEN Answer <- EVEN Input N Remainder = 0? Output Answer Structured Programming 14 Yes Start Remainder <- N modulo 2 End No Answer <- ODD

15 Programming Style Standard form int main( ) { program statements in here; return 0; } Remark: At the end of the program, Zero is usually returned to indicate error-free function termination. clarity and ease in reading Structured Programming 15

16 Programming Style (cont.) Poor programming style int main ( ) { printf ( Hello there world! ); return 0;} difficult to read and understand Structured Programming 16

17 Comments are explanatory remarks made within a program have no effect on program execution start of comment with /* end of comment via */ Example /* this is a comment */ /* this program prints out a message */ Structured Programming 17

18 Pgm1-3.cpp & Output Comment Output Structured Programming 18

19 The printf( ) Function Structured Programming 19

20 Pgm1-1.cpp & Output printf( ) Preprocessor command Output Structured Programming 20

21 Preprocessor Command Begin with a pound sign #, do not end with ; e.g. #include<stdio.h> The first step in the C program compilation stage The #include preprocessor command causes the contents of header file in <> to be inserted where the #include command appears Structured Programming 21

22 C Libraries - #include Library file #include <stdio.h> #include <io.h> #include <math.h> #include <string.h> Functions Standard I/O functions printf, scanf, getc, fopen, fclose Traditional file operations lock, create, filelength, read, write Arithmetic abs, floor, pow, sqrt Logarithmic log, exp, Trignometric sin, tan, cos, atan Floating point fabs, fmod String operations strcpy, strcat, strcmp, strlen, strrev, strlwr, strupr Without including these libraries, you cannot write C programs that need to use these standard function. Check your reference for details on the C libraries, their functions and how they can be used Structured Programming 22

23 Pgm1-2.cpp & Output new line: \n Output Structured Programming 23

24 \n If the backslash was omitted from the second printf( ) call in Pgm1-2.cpp Original Output New Output (without \) Structured Programming 24

25 An Example of \n Output Structured Programming 25

26 Common Programming Errors Omitting the parentheses after main main main( ) Omitting or incorrectly typing the opening brace { that signifies the start of a function body Omitting or incorrectly typing the closing brace } that signifies the end of a function Misspelling the name of a function print( ) printf( ) Structured Programming 26

27 Common Programming Errors (cont.) Forgetting to close the message to printf( ) with a double quote ( ) symbol Omitting the semicolon (;) at the end of each statement Forgetting the \n to indicate a new line Structured Programming 27

28 Introduction to Modularity Structured Programming 28

29 Introduction to Modularity (cont.) Structured Programming 29

30 Functions Structured Programming 30

31 Functions (cont.) The names permissible for functions are referred to as identifiers Rules first character of the name must be a letter or underscore ( _ ) only letters, digits, or underscores may follow the initial letter cannot be one of the keywords may have no more than 31 characters Structured Programming 31

32 Keywords (Reserved Words) Structured Programming 32

33 An Example of Valid & Invalid C Identifiers grosspay taxcalc addnums DegToRad 1AB3 salestax netpay while multtwo E*6 bessel1 Case-sensitive language TOTAL, total, TotaL three distinct names Structured Programming 33

34 The main( ) Function Structured Programming 34

35 The main( ) Function (cont.) Structured Programming 35

36 A Sample main( ) Function Structured Programming 36

37 Top-Down Program Development The five steps in the top-down development procedure Step1: determine the desired output Step2: determine the input items Step3: design the program determine an algorithm do a hand calculation Step4: write the program Step5: test the output Structured Programming 37

38 An Example of Problem The circumference, C, of a circle is given by the formula C = 2 r, where is the constant (accurate to four decimal places), and r is the radius of the circle. Using this information, write a C program to calculate the circumference of a circle that has a 2-inch radius Structured Programming 38

39 Step1: Determine the Desired Output calculate, print, determine, find, or compare can be used to determine the desired output to calculate the circumference of a circle Structured Programming 39

40 Step2: Determine the Input Items input item is the name of an input quantity input value is a specific number input item the radius of the circle input value Structured Programming 40

41 Step3: Design the Program consists of 2 steps determine an algorithm (pseudocode) Assign a value to r Calculate the circumference using the formula C = 2 r Display the result do a hand calculation substitute radius of 2 inches into the formula 2(3.1416)2 = inches Structured Programming 41

42 Pgm1-4.cpp & Output Calculate the circumference of the circle Output Structured Programming 42

43 Step5: Test the Output is to verify that a program works correctly and fulfills its requirements The same program can be used over and over with new input data Program error is called a bug Debugging includes locating, correcting, and verifying the correction Structured Programming 43

44 Modularity & Top-Down Design Structured Programming 44

45 Modularity & Top-Down Design (cont.) Structured Programming 45

46 Program Translation Structured Programming 46

47 Program Translation (cont.) Interpreter each statement in the source program is translated individually and executed immediately Compiler all the statements in the source program are translated before any one statement is executed The result of compiling a source program is called an executable program Structured Programming 47

48 Chapter Summary main( ) printf( ) The body of function { All program statements in here; } Structured Programming 48

49 Chapter Summary (cont.) All C statements must be terminated by a semicolon (;) printf( ) can be a message enclosed with double quotes printf( Hello there world! ); Structured Programming 49

50 Q&A Structured Programming 50

51 Practice Write algorithm to solve the following: input 5 numbers and display how many odd numbers and how many even numbers. Example: If I input 5, 8, 9, 4, 7 The number of odd is 3 The number of even is Structured Programming 51