Chapter 1- C++ programming languages +.ppt
- 1. Chapter 1 Introduction to Programming
- 2. Introduction What is a computer? A Computer is an electronic device that accepts data, performs computations, and makes logical decisions according to instructions that have been given to it; then produces meaningful information in a form that is useful to the user. Inputs Process Outputs
- 3. What is a program? Computer programs, software programs, or just programs are the instructions that tells the computer what to do. Computer programming (programming or coding) is the process of writing, testing, debugging/troubleshooting, and maintaining the source code of computer programs
- 4. Intro A computer program consists of two elements: Code – action Data – characteristics Computer programs (also know as source code) is often written by professionals known as Computer Programmers. Source code is written in one of programming languages.
- 5. Programming language A programming language is an artificial language that can be used to control the behavior of a machine, particularly a computer. Programming languages, like natural language, are defined by syntactic and semantic rules which describe their structure and meaning respectively. The syntax of a language describes the possible combinations of symbols that form a syntactically correct program. The meaning given to a combination of symbols is handled by semantics.
- 6. Programming language A main purpose of programming languages is to provide instructions to a computer. Available programming languages come in a variety of forms and types. Programming languages can be divided in to two major categories: Low-level languages High-level languages
- 7. Low-level Languages Machine language It is the lowest level programming language in which all instructions and data are written in a binary machine code, i.e. 0s and 1s. Computers only understand one language and that is binary language or the language of 1s and 0s. For example: 00101010 000000000001 000000000010 10011001 000000000010 000000000011 In the initial years of computer programming, all the instructions were given in binary form. Although the computer easily understood these programs, it proved too difficult for a normal human being to remember all the instructions in the form of 0s and 1s. Therefore, computers remained mystery to a common person until other languages such as assembly language was developed, which were easier to learn and understand.
- 8. Low-level language Assembly language correspondences symbolic instructions and executable machine codes and was created to use letters (called mnemonics) to each machine language instructions to make it easier to remember or write. For example: ADD A, B – adds two numbers in memory location A and B However, no matter how close assembly language is to machine code, computers still cannot understand it. The assembly language must be translated to machine code by a separate program called assembler. The machine instruction created by the assembler from the original program (source code) is called object code. Thus assembly languages are unique to a specific computer (machine).
- 9. High-level Languages Use naturally understandable languages IDE’s are used for rapid development like C++, .Net environment they permitted a programmer to ignore many low-level details of the computer's hardware. closer the syntax, rules, and mnemonics to "natural language“. High-level languages are more English-like and, therefore, make it easier for programmers to "think" in the programming language.
- 10. High-level language High-level languages also require translation to machine language before execution. This translation is accomplished by either a compiler or an interpreter. Compilers translate the entire source code program before execution. Interpreters translate source code programs one line at a time. Interpreters are more interactive than compilers. E.g, FORTRAN (FORmula TRANslator), BASIC (Bingers All Purpose Symbolic Instruction Code), PASCAL, C, C++, Java.
- 11. Programming paradigms Procedural Programming Languages Object-Oriented Programming Languages
- 12. Procedural Programming Languages is a list of instructions telling a computer, step-by-step, what to do, usually having a linear order of execution from the first statement to the second and so forth. Procedural programming specifies a list of operations that the program must complete to reach the desired state. Each program has a starting state, a list of operations to complete, and an ending point. This approach is also known as imperative programming. Procedures, also known as functions, subroutines, or methods, are small sections of code that perform a particular function. A procedure is effectively a list of computations to be carried out. By splitting the programmatic tasks into small pieces, procedural programming allows a section of code to be re-used in the program without making multiple copies. E.g. FORTRAN and BASIC.
- 13. Object-Oriented Programming Languages Object-oriented programming is one the newest and most powerful paradigms. Object-oriented programming is a programming paradigms based on the concept of objects, which are data structures that contains data in the form of fields, known as attributes and code in the form of procedures known as method. This pairing of a piece of data with the operations that can be performed on it is known as an object. A program thus becomes a collection of cooperating objects, rather than a list of instructions. Objects can store state information and interact with other objects, but generally each object has a distinct, limited role.
- 14. Problem Solving Techniques Computer solves varieties of problems that can be expressed in a finite number of steps leading to a precisely defined goal by writing different programs. A program is not needed only to solve a problem but also it should be reliable, (maintainable) portable and efficient. In computer programming two facts are given more weight: The first part focuses on defining the problem and logical procedures to follow in solving it. The second introduces the means by which programmers communicate those procedures to the computer system so that it can be executed.
- 15. Cont’d There are system analysis and design tools, particularly flowchart and structure chart, that can be used to define the problem in terms of the steps to its solution. The programmer uses programming language to communicate the logic of the solution to the computer. Before a program is written, the programmer must clearly understand what data are to be used, the desired result, and the procedure to be used to produce the result. The procedure, or solution, selected is referred to as an algorithm. An algorithm is defined as a step-by-step sequence of instructions that must terminate and describe how the data is to be processed to produce the desired outputs.
- 16. Algorithms Simply, algorithm is a sequence of instructions. Algorithms are a fundamental part of computing. An algorithm must satisfy the following requirements: Unambiguousness: i.e. it must not be ambiguous. Every step in an algorithm must be clear as to what it is supposed to do and how many times it is expected to be executed. Generality: i.e. it should have to be general, not to be specific. Correctness: it must be correct and must solve the problem for which it is designed. Finiteness: it must execute its steps and terminate in finite time. Algorithms are usually represented in pseudo code or by a flow chart.
- 17. Pseudocodes is English like language for representing the solution to a problem. Pseudo code is independent of any programming language. Pseudo code (or a flow chart) is the first step in the process of planning the solution to a problem (also called developing an algorithm). Pseudo code is a compact and informal high-level description of a computer algorithm that uses the structural conventions of programming languages, but typically omits details such as subroutines, variables declarations and system-specific syntax. The purpose of using pseudocode is that it may be easier for humans to read than conventional programming languages No standard for pseudocode syntax exists, as a program in pseudocode is not an executable program.
- 18. Pseudocode As the name suggests, pseudocode generally does not actually obey the synatx rules of any particular language; there is no systematic standard form, although any particular writer will generally borrow the appearance of a particular language. The programming process is a complicated one. You must first understand the program specifications, of course, Then you need to organize your thoughts and create the program. This is a difficult task when the program is not trivial (i.e. easy). You must break the main tasks that must be accomplished into smaller ones in order to be able to eventually write fully developed code. Writing pseudocode will save you time later during the construction & testing phase of a program's development.
- 19. Example: Original Program Specification: Write a program that obtains two integer numbers from the user. It will print out the sum of those numbers. Pseudo code: Prompt the user to enter the first integer Prompt the user to enter a second integer Compute the sum of the two user inputs Display an output prompt that explains the answer as the sum Display the result • If student's grade is greater than or equal to 60 Print "passed" else Print "failed"
- 20. Flowcharts A flowchart is a graphical way of representing the solution to a problem The advantage of flowchart is it doesn’t depend on any particular programming language, so that it can used, to translate an algorithm to more than one programming language. Flowchart uses different symbols (geometrical shapes) to represent different processes.
- 22. Example 1: Draw flow chart of an algorithm to add two numbers and display their result. Algorithm description Read the rules of the two numbers (A and B) Add A and B Assign the sum of A and B to C Display the result ( c)
- 24. Example 2 Write an pseudo code and draw a flow chart to check a number is negative or not.
- 25. Algorithm description. 1. Start 2. Read a number x 3. If x is less than zero then Write “Negative” Else Write “Not Negative” 4. stop
- 26. Example 3 Write the algorithm description (Pseudo code) and Draw flow chart of an algorithm to find the following sum. Sum = 1+2+3+…. + 50 Algorithm description (Pseudo code) 1. Start 2. Initialize Sum to 0 and Counter to 1 2.1 If the Counter is less than or equal to 50 • Add Counter to Sum • Increase Counter by 1 • Repeat step 2.1 2.2 Else • Exit Loop 3. Write Sum 4. Stop
- 28. Exercise: 1. Write an algorithm description and draw a flow chart to check a number is even or odd.