Bài giảng Introduction to Computer Programming (C language) - Chapter 1: Introduction to Computers and Programming - Võ Thị Ngọc Châu

 Ho Chi Minh City University of Technology 
 Faculty of Computer Science and Engineering 
 Chapter 1: Introduction to 
Computers and Programming 
 Introduction to Computer Programming 
 (C language) 
 TS. Võ Thị Ngọc Châu 
 (chauvtn@cse.hcmut.edu.vn, 
 chauvtn@hcmut.edu.vn) 
 2017 – 2018, Semester 2 
Course Content 
 C.1. Introduction to Computers and 
 Programming 
 C.2. C Program Structure and its 
 Components 
 C.3. Variables and Basic Data Types 
 C.4. Selection Statements 
 C.5. Repetition Statements 
 C.6. Functions 
 C.7. Arrays 
 C.8. Pointers 
 C.9. File Processing 2 
 References 
 [1] “C: How to Program”, 7th Ed. – Paul 
 Deitel and Harvey Deitel, Prentice Hall, 2012. 
 [2] “The C Programming Language”, 2nd Ed. 
 – Brian W. Kernighan and Dennis M. Ritchie, 
 Prentice Hall, 1988 
 and others, especially those on the Internet 
 3 
Content 
 Introduction 
 Computer Organization 
 Programming Languages 
 Programming Tasks 
 Data and Algorithms 
 Summary 
 4 
Introduction 
 Computer Programming 
  Computer 
 a device that can perform computations and make 
 logical decisions billions of times faster than human 
 beings can 
  Programming 
 The act of writing the programs executable on the 
 computers to produce intended results 
  Program 
 A sequence of instructions written in a programming 
 language to perform a specified task by the computer 
 5 
Introduction 
 Programs and 
 Computers Programming their Results 6 
Computer Organization 
 Hardware: physical components of 
 computer (including peripherals) 
  the keyboard, screen, mouse, hard disk, 
 memory, DVDs and processing units,  
 Software: a set of machine-readable 
 instructions that directs a computer's 
 processor to perform specific operations 
 [Wikipedia] 
  Application softwares 
  Operating system 
  System softwares 
 7 
 Computer Organization - 
 Hardware 
 Computer Architecture 
ALU = Arithmetic/logic gate unit: performing 
arithmetic and logic operations on data 8 
Computer Organization – 
Software 
 9 
Programming Languages 
 Programming language: a formal language 
 for writing a computer program as a 
 sequence of instructions 
  C, C++, C#, Java, PHP, Python,  
 Three general types 
  Machine languages 
  Assembly languages 
  High-level languages 
 Providing a sequence of instructions that directly 
 understandable by computers or requiring some 
 intermediate translation steps 
 10 
Programming Languages – 
Machine Languages 
 First-generation language: strings of 
 numbers (ultimately reduced to 1s and 0s) 
 that instruct computers to perform their 
 most elementary operations one at a time 
  Directly understandable by computers 
  Machine-dependent 
 For example, instructions for 
 adding overtime pay to base 
 pay and then storing the 
 result in gross pay 
 11 
Programming Languages – 
Assembly Languages 
 Second-generation language: a low-level 
 language used to interface with computer 
 hardware using English-like abbreviations 
 to represent elementary operations 
  Less understandable by computers 
  Need for translation steps to convert an 
 assembly language program to machine codes 
 Translator = Assembler 
 For example, instructions for 
 adding overtime pay to base 
 pay and then storing the 
 result in gross pay 12 
 Programming Languages – 
 High-level Languages 
 Third-generation language: written 
 instructions that look almost like everyday 
 English and contain commonly used 
 mathematical notations 
  Less understandable by computers 
  Translator program is called compiler. 
  The C language is a high-level language that needs 
 a compiler. 
  Scripting languages such as PHP and Perl need an 
 interpreter. 
 For example, instructions for adding overtime pay to base pay and 
 then storing the result in gross pay: grosspay = basepay + overpay. 13 
 Programming Languages – 
 High-level Languages 
Program File Compiler Binary File CPU Result 
C, C++, Java,  
Program File Interpreter CPU Result 
PHP, Perl,  
 A history of computer programming languages – Wikipedia 
 Graph of programming language history – www.levenez 
 14 
Programming Languages – 
The C language 
 Evolved from B by Dennis Ritchie at Bell 
 Laboratories and originally implemented on 
 a DEC PDP-11 computer in 1972 
 Using many of the important concepts of 
 BCPL and B while adding data typing and 
 other powerful features 
 Used for many important application trends 
  Developing new major operating systems: UNIX, 
 Linux, Android,  
  Developing programs in the embedded systems 
 in cars, medical machines,  
 15 
Programming Languages – 
The C language 
 Ken Thompson (left) with Dennis Ritchie (right, 
 the inventor of the C programming language) 
 [Wikipedia] 
 The development of the C language 
  Dennis M. Ritchie 
 Full history of the C language 
  Wikipedia 
 16 
Programming Tasks 
Design of Library Library 
 program (Header: *.h) (Object code: *.lib; *.dll; *.so) 
 Editor Preprocessor Compiler Linker Executable 
 Program 
 Source code Enhanced source code Object code 
 *.h + *.c *.h + *.c (*.cpp) *.obj 
 (*.cpp) 
 gcc; g++ 
 Integrated Development Environment (IDE): 
 Visual Studio; Eclipse; Qt Creator; Code block; Online tool; etc 
 17 
Programming Tasks 
 Editor: supports text editing feature for 
 writing source code 
 Preprocessor: preprocesses the source code 
 with replacing macro, inserting library files 
 *.h,  
 Compiler: translates the source code into 
 target machine language 
 Linker: links the object code to other library 
 files 
 18 
 Data and Algorithms – 
 Concepts 
 Program 
= A Sequence of Instructions Written in a 
Programming Language to Perform a Specified 
Task by the Computer 
= Data and their Structures + Algorithms 
 Input/Output/ Process 
 Example 1: instructions for adding overtime pay to base pay and 
 then storing the result in gross pay: grosspay = basepay + overpay. 
 Example 2: given n positive numbers, find the smallest one. 
 19 
Data and Algorithms – 
Data 
 Atomic data: int, double, char, ... 
 Non-atomic data: array, struct, enum,  
 A strong relationship between the data 
 structures and the operations on the data in 
 the corresponding structures 
 Example 1: instructions for adding overtime pay to base pay and 
 then storing the result in gross pay: grosspay = basepay + overpay. 
 - Input Data: basepay and overpay are positive real numbers 
 (double). 
 - Output Data: grosspay is also a positive real number (double). 
 Example 2: given n positive numbers, find the smallest one. 
 - Input Data: n positive real numbers are treated individually OR as 
 a collection (double) 
 - Output Data: minNumber is a positive real number (double). 20 
Data and Algorithms – 
Algorithms 
 Algorithm = a sequence of unambiguous 
 instructions for solving a problem, i.e. for 
 obtaining a required output for any 
 legitimate input in a finite amount of time 
  Anany Levitin, Introduction to the Design and 
 Analysis of Algorithms, 2nd Edition, Addison 
 Wesley, 2007 
 Algorithm representation 
  Pseudo code 
  Flowchart 
  Real code in a high-level programming language 
 21 
 Data and Algorithms – 
 Algorithms 
 Example 2: given n positive numbers, find the 
 smallest one. 
 Task solution: 
  1. Suppose that the first number is the smallest one 
 (current one). 
  2. Check if the current smallest one is a real one as 
 compared to the next number. 
 If yes then compared to the next number of the next one 
 like step 2 till all numbers are checked. 
 Otherwise, 
 . update the smallest one with the smaller one 
 . And then move next to check with the next number of the 
 next number like step 2 till all numbers are checked. 22 
Data and Algorithms – 
Algorithms – Pseudo Code 
 Header 
  Algorithm name Header 
  Input data and their data types 
  Task purpose 
 Body 
  Pre-conditions 
  Post-conditions 
  Output data and their data types 
 Body 
  (Numbered) (control) statements 
  Comments 
 23 
 Data and Algorithms – 
 Algorithms – Pseudo Code 
 Algorithm findMinNumber 
 Example - Input: positiveNumber[n] which is an array of n positive double values 
 - Output: minNumber which is the smallest one whose type is double 
 2: given - Purpose: find the smallest number in a collection 
 - Precondition: n data inputs are positive. 
 n positive Begin Algorithm 
 Check positiveNumber[n] contains only positive values 
 numbers, minNumber = positiveNumber[1] 
 iteration = 2 
 find the While (iteration <= n) 
 smallest Begin While 
 If (minNumber <= positiveNumber[iteration]) Then 
 one. iteration = iteration + 1 
 Else 
 Begin 
 minNumber = positiveNumber[iteration] 
 iteration = iteration + 1 
 End 
 End While 24 
 End Algorithm 
Data and Algorithms – 
Algorithms – Flowchart 
 Symbols used for drawing a flowchart 
 25 
Data and Algorithms – 
Algorithms - Flowchart 
 Terminal: starting point or end point 
 Input/Output: input data/output data of the 
 algorithm 
 Flow line: shows a control flow of the 
 algorithm. Execution follows this part. 
 Decision: allows a condition (expressed as 
 a boolean expression) to be checked 
 Process: data processing block 
 26 
Data and Algorithms – 
Algorithms - Flowchart 
 Predefined process: an existing data 
 processing block 
 On-page connector: a gathering point of 
 the flow lines in a flowchart 
 Off-page connector: a gathering point of 
 the flow lines from another page 
 Preparation: preparation steps, setting for 
 initial conditions 
 Annotation: comments 
 27 
Data and Algorithms – 
Algorithms - Flowchart 
 false 
 true 
 if Statement 
 28 
Data and Algorithms – 
Algorithms - Flowchart 
 false 
 true 
 if-else Statement 29 
Data and Algorithms – 
Algorithms - Flowchart 
 false false false 
 true true true 
 switch-case Statement 
 30 
Data and Algorithms – 
Algorithms - Flowchart 
 false 
 true 
 <Iteration Value 
 Modification> 
 for Statement 
 31 
Data and Algorithms – 
Algorithms - Flowchart 
false 
 true 
 true 
 false 
 while Statement do while Statement 
 32 
 Flowchart vs. Pseudo Code? 
 Example 2: minNumber = How to add the checking 
 positiveNumber[1] 
 given n of n positive numbers? 
 positive iteration = 2 
 numbers, 
 false 
 iteration <= n 
 find the 
 smallest true 
 minNumber<= true 
 one. iteration = 
 positiveNumber[iteration] 
 iteration + 1 
 false 
 minNumber = 
 positiveNumber[iteration] 
 33 
 Data and Algorithms – 
 Algorithms – Real code in C 
void main() { 
 double positiveNumber[10] = {2, 1, 3, 10, 8, 3, 4, 5, 9, 12}; 
 int n = 10; 
 How to add the checking 
 double minNumber = positiveNumber[0]; of n positive numbers? 
 int iteration = 1; 
 while (iteration < n) { 
 if (minNumber <= positiveNumber[iteration]) iteration = iteration + 1; 
 else { 
 minNumber = positiveNumber[iteration]; 
 iteration = iteration + 1; 
 } 
 } 
} Pseudo Code vs. Flowchart vs. Real Code in C? 34 
Summary 
 Concepts related to computer programming 
 Short introduction to computers, programs, 
 programming, and programming languages 
 Short introduction to the C language 
 Preparation for computer programming 
  Programming tasks 
  Data and basic data types 
  Algorithms and their representations 
 35 
Chapter 1: Introduction to 
Computers and Programming 
 36