![My First C Program
Jane Doe*/
January 29, 2020 */
1. /* Programmer:
2. /* Date:
3.
4. #include <stdio.h>
5.
6. int main(int argc, char
*argv[]) 7. {
8. printf(“Hello, World!n”);
9. return 0;
10. }](https://image.slidesharecdn.com/cse1201lecture1introductiontoprogramming0fd134f8149173dfa0821f1575f733a1-240907155843-777928ae/85/CSE_1201_Lecture_1_Introduction_to_Programming_0fd134f8149173dfa0821f1575f733a1-pdf-pptx-21-320.jpg)
![• Lines 1 & 2: /* Programmer:
/* Date:
Jane Doe */
January 29, 2020 */
Comments are enclosed in /* … */ constructs. The first two lines provide
useful information about the person who wrote the program, in addition to the date on
which it was written.
• Line 4: #include <stdio.h>
As part of compilation, the C compiler runs a program called the C preprocessor.
The preprocessor adds and removes code from your source file. In this case, the
directive #include tells the preprocessor to include code from the file stdio.h. This file
contains declarations for functions and symbolic constants that the program needs to
use. A
declaration for the printf function is in this file.
• Line 6: int main(int argc, char *argv[])
This statement declares the main function. A C program can containmany functions
but must always have one main function, which is the entry point into the program. A
function is a self-contained module of code that can accomplish some task. The “int"
specifies the return type the function. In this case, an Integer value is returned to the
operating system.](https://image.slidesharecdn.com/cse1201lecture1introductiontoprogramming0fd134f8149173dfa0821f1575f733a1-240907155843-777928ae/85/CSE_1201_Lecture_1_Introduction_to_Programming_0fd134f8149173dfa0821f1575f733a1-pdf-pptx-23-320.jpg)
CSE_1201_Lecture_1_Introduction_to_Programming_0fd134f8149173dfa0821f1575f733a1.pdf.pptx
- 1. CSE 1201 Introduction to Programming - in C Lecture 1 Programming is to Computer Science as Mathematics is to Physics
- 2. Introduction • Lecturers – Instructors: Ms. Aurel Liddell (Room E27) Mr. Lenandlar Singh Mr. Rayad Lakhan Mr. Renard Jacobis, Mr. Kim Shing Chong* 3 hrs/week 2 hrs/week – Tutors (labs): • Lectures • Laboratory session • Recommended Texts: – The C Programming Language by Kernighan and Ritchie – C Programming: A Modern Approach by K.N. King • Assessments*: – Individual Assignments/ Labs quizzes – 1 Group Project – 2 In-class tests – Final Exam 10% 10% 20% 60% * subject to change
- 3. Learning Outcomes At the end of this course, you will be able to: 1. Identify the basic terminology used in computer programming 2. Explain the process and tools used in transforming source code into executable programs 3. Differentiate between programming language paradigms 4. Write, compile and debug programs in C language. 5. Use different data types in a computer program. 6. Design programs involving decision structures, loops and functions. 7. Explain the difference between call by value and call by reference 8. Discuss the dynamics of memory by the use of pointers. 9. Make appropriate decisions about when to use macros vs functions 10. Use different data structures and create/update basic data files. 11. Explain the difference between computer programming and software engineering
- 4. Outline of Today’s Topics • Software Categories • The Evolution of Programming Languages • History of the C Programming Language • What happens to your program? – Compilation, Linking, Execution
- 5. A Layered View of the Computer Application Programs Word-Processors, Spreadsheets, Database Software, IDEs, etc… System Software Compilers, Interpreters,Preprocessors, etc. Operating System, Device Drivers Machine with all its hardware
- 6. Software Categories • Application S/w – Programs written for computer users • Word-processors, spreadsheets, & other application packages • System S/w – Programs written for computer systems • Compilers, operating systems, utility programs, programming languages …
- 7. Software Categories cont’d System S/w: The Operating System (OS) Provides several essential services: – Loading & running application programs – Allocating memory & processor time – Providing input & output facilities – Managing files of information – Manages low-level interaction with hardware
- 8. What is Computer Programming? • Involves writing instructions for the computer hardware to execute • The aim is to achieve the outcome of some task quickly and accurately while producing the same results every time, given the same input. • Performed using a suitable programming language
- 9. What is a Programming Language? • A vocabulary and set of grammatical rules for instructing a computer to perform specific tasks • Each language has a unique set of keywords (words that it understands) and a special syntax for organizing program instructions. • Programs are converted into machine language so that the computer can understand it. There are two ways to do this: – compile the program – interpret the program
- 10. The Evolution of Programming Languages • Machine Language (1940s & ‘50s) – Uses binary code – Machine-dependent – Not portable • Assembly Language (1950s & ‘60s) – Uses mnemonics – Machine-dependent – Not usually portable • High-Level Language – Uses English-like language – Machine independent – Portable (but must be compiled for different platforms) – Examples: Fortran, Pascal, C, C++, Java, etc.
- 11. Machine Language • The representation of a computer program which is actually read and understood by the computer. – A program in machine code consists of a sequence of machine instructions. • Instructions: – Machine instructions are in binary code – Instructions specify operations and memory cells involved in the operation Example: Operation Address 0010 0000 0000 0100 0100 0000 0000 0101 0011 0000 0000 0110
- 12. Assembly Language • A mnemonic representation of the machine language of a specific processor. • Example: Load Add Store Price Tax Cost • Is converted to machine code by an assembler. • Usually, each line of assembly code produces one machine instruction (One-to-one correspondence). • Programming in assembly language is slow and error-prone but is more efficient in terms of hardware performance. • It forced the programmer to think in terms of the machine rather than in terms of his/her problem.
- 13. High-level language • Developed in the late 1950s & ‘60s • A programming language which uses statements consisting of English- like keywords such as "FOR", "PRINT" or “IF“, ... etc. • Each statement corresponds to several machine language instructions (one- to-many correspondence). • The idea was to allow the programmer to think about a problem in terms familiar to him/her and relevant to the problem rather than have to worry about the machine.
- 14. High-level language • Data referenced using descriptive names • Operations can be described using familiar symbols • Example: Cost := Price + Tax • A program called a compiler is used to translate a program written in a high- level language to machine language.
- 15. The History of C • Unix was originally written in Assembly language. • Ken Thompson wrote B as a higher level language to enhance Unix. • However, B was ineffective. • In 1971 Dennis Ritchie at Bell Laboratories extended B calling it ‘NB’ (newB) • In 1972-3, ‘NB’ was redesigned and renamed ‘C’ • Originally used to rewrite the UNIX operating system. • First versions known as “Traditional C” or “Classic C” • Standardised version approved in 1989 and now called “ANSI C” (actual standardisation work started in 1983)
- 16. The History of C cont’d • Many new languages are based off of C: – C++ – Java – C# – Perl • Today, virtually all major operating systems are written in C and/or C++ • Apart from system s/w, C is also used to write application s/w such as word processing programs, spreadsheet programs, database management programs, accounting programs, games, educational software, etc.
- 17. Characteristics of C • Lies just above Assembly Language and just below High Level Languages such as BASIC, PASCAL and FORTRAN in the Programming Language type hierarchy • C is a compiled language • 32 keywords in “ANSI C” and a rich collection of existing functions (operations/procedures) called the “C Standard Library” • C is case sensitive. That is, the same letter in lowercase or uppercase is treated as being different • Simple, flexible, loose procedural language, but requires attention to detail. Easy to make mistakes • Executable produced are fast (when compared with programs written in languages such as Visual Basic, Fox Pro, Java etc.) • Used to implement solutions for a wide variety of programming problems • C is hardware-independent and highly portable. That is, the same carefully designed
- 18. The C Standard Library • A rich collection of pre-written functions • There are two primary aspects to learning C – Learning the C language itself – Learning how to use the functions in the C Standard Library (encourages software reusability) • The C Standard Library is the foundation of “building blocks” - the collections of functions - that make up C programs • C programs usually consist of the following functions: – Those from The C Standard Library – Functions you create yourself – Functions other people have created and made available to you
- 19. The Software Development Life Cycle 1. Define/Understand problem 2. Analyse problem to obtain requirements 3. Design solution(s): Components, Storage Mechanism, Interface and Algorithms 4. Programming: use suitable programming language to transform design into executable computer program 5. Test: run executable to determine if program solves problem and satisfies requirements 6. Deploy application: hand over program to users 7. Maintenance: corrective, preventative and perfective
- 20. The Programming Life Cycle 1. Understand problem 2. Decompose problem into manageable units (top-down stepwise refinement is recommended) 3. Design algorithm, flowchart and pseudo code, and storage mechanism for solution 4. Encode algorithm using an appropriate programming language 5. Compilation: use appropriate compiler to compile computer program into executable program (involves linking etc) 6. Testing: Test module/function to determine if it satisfies requirments. Also know as unit testing 7. Repeat 3 – 6 as required.
- 21. My First C Program Jane Doe*/ January 29, 2020 */ 1. /* Programmer: 2. /* Date: 3. 4. #include <stdio.h> 5. 6. int main(int argc, char *argv[]) 7. { 8. printf(“Hello, World!n”); 9. return 0; 10. }
- 22. The Anatomy of a C program
- 23. • Lines 1 & 2: /* Programmer: /* Date: Jane Doe */ January 29, 2020 */ Comments are enclosed in /* … */ constructs. The first two lines provide useful information about the person who wrote the program, in addition to the date on which it was written. • Line 4: #include <stdio.h> As part of compilation, the C compiler runs a program called the C preprocessor. The preprocessor adds and removes code from your source file. In this case, the directive #include tells the preprocessor to include code from the file stdio.h. This file contains declarations for functions and symbolic constants that the program needs to use. A declaration for the printf function is in this file. • Line 6: int main(int argc, char *argv[]) This statement declares the main function. A C program can containmany functions but must always have one main function, which is the entry point into the program. A function is a self-contained module of code that can accomplish some task. The “int" specifies the return type the function. In this case, an Integer value is returned to the operating system.
- 24. • Line 7: { This opening bracket denotes the start of the program. It is used to denote the beginning of a block of program statements. • Line 8: printf("Hello, World!n"); printf is a function from a standard C library that is used to print strings to the standard output, normally your screen. The compiler links code from these standard libraries to the code you have written to produce the final executable. The n code tells the printf function to advance to the next line after printing the message. • Line 9: return 0; This statement that tells the calling program - the loader (a program run by the Operating System) that the program/function was ended successfully. • Line 10: } Closing bracket denotes the end of the main function block (and end of the program).
- 25. What happens when we run a C program? The Life Cycle of a C Program
- 26. Transforming a C program into an executable. 1. Editor / IDE: A program is written in a text editor, e.g. Notepad then saved with a ‘.c’ extension. The file produced is called the source code. 2. Preprocess : The source code is passed to the preprocessor according to the preprocessor directives. Preprocessor directives begin with a hash sign (#), such as #include and #define. They indicate that certain manipulations are to be performed BEFORE compilation. A typical manipulation would be to include in the source code, the contents of the file defined by #include <filename> (Typically #include references header files which contain the declaration of functions and other objects). The preprocessor is also responsible for removing comments from the source code.
- 27. Transforming a C program into an executable. 3. Compile: The preprocessed file is then passed to a program called the C Compiler which translates the source code into machine readable code. Compilation involves analyzing the language structure of the source code to determine if it is valid. Once no errors are detected, the compiler generates a binary file called an object code file (aka ‘.o’ or ‘.obj’ file) and stores it on disk. If any compiler errors are received, no object code file will be generated. However, if only warnings were received, an object code file will be generated. Object code is not directly executable, though. In order to make an executable, the implementation code for all of the library functions that were #included into the file need to be added in. This is the job of the linker.
- 28. Transforming a C program into an executable. 3. Compile cont’d: During compilation, the Compiler checks for objects or functions that were not locally defined in the source code, for example, the printf() function. It then produces an entry in the object code file's symbol table saying that printf() has an “unresolved reference” (or simply that no implementation of the function was found). 4. Linker: The object file is then passed to the Linker which sees the unresolved reference to undefined objects or functions such as printf() and searches the available libraries for their implementation. When found, it links those unresolved references to their corresponding library implementation and produces an executable file (.out or .exe file) and stores it on disk. If any linker errors are received, no executable file will be generated.
- 29. Transforming a C program into an executable. 5. Loader: The loader puts the executable file in memory. 6. CPU: The CPU takes the executable and runs each instruction until the program is fully executed.
- 30. A gentle conclusion That's it!!! To get the most out of this class, you should get access to both a text editor and a C compiler. A C compiler, Borland Dev C++, is available in the Computer Science Laboratory. Dev C++ comes with a text editor and compiler. Otherwise, use one of the text editors, installed on your computer or try an online complier. Instructions for practicing your first program will be covered in the first laboratory session.