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2017/8/26 Computer Programming Quick Guide COMPUTER PROGRAMMING - QUICK GUIDE https://www.tutorialspoint.com/computer_programming/computer_programming_quick_guide.htm Copyright © tutorialspoint.com COMPUTER PROGRAMMING - OVERVIEW Introduction to Computer Program Before getting into computer programming, let us first understand computer programs and what they do. A computer program is a sequence of instructions written using a Computer Programming Language to perform a specified task by the computer. The two important terms that we have used in the above definition are − Sequence of instructions Computer Programming Language To understand these terms, consider a situation when someone asks you about how to go to a nearby KFC. What exactly do you do to tell him the way to go to KFC? You will use Human Language to tell the way to go to KFC, something as follows − First go straight, after half kilometer, take left from the red light and then drive around one kilometer and you will find KFC at the right. Here, you have used English Language to give several steps to be taken to reach KFC. If they are followed in the following sequence, then you will reach KFC − 1. 2. 3. 4. 5. Go straight Drive half kilometer Take left Drive around one kilometer Search for KFC at your right side Now, try to map the situation with a computer program. The above sequence of instructions is actually a Human Program written in English Language, which instructs on how to reach KFC from a given starting point. This same sequence could have been given in Spanish, Hindi, Arabic, or any other human language, provided the person seeking direction knows any of these languages. Now, let's go back and try to understand a computer program, which is a sequence of instructions written in a Computer Language to perform a specified task by the computer. Following is a simple program written in Python programming Language − "Hello, World!" The above computer program instructs the computer to print "Hello, World!" on the computer screen. A computer program is also called a computer software, which can range from two lines to millions of lines of instructions. https://www.tutorialspoint.com/cgi-bin/printpage.cgi 1/63 p r i n t

2017/8/26 Computer Programming Quick Guide Computer program instructions are also called program source code and computer programming is also called program coding. A computer without a computer program is just a dump box; it is programs that make computers active. As we have developed so many languages to communicate among ourselves, computer scientists have developed several computer-programming languages to provide instructions to the computer . We will see several computer programming languages in the subsequent chapters. Introduction to Computer Programming If you understood what a computer program is, then we will say: the act of writing computer programs is called computer programming. As we mentioned earlier, there are hundreds of programming languages, which can be used to write computer programs and following are a few of them − Java C C++ Python PHP Perl Ruby Uses of Computer Programs Today computer programs are being used in almost every field, household, agriculture, medical, entertainment, defense, communication, etc. Listed below are a few applications of computer programs − MS Word, MS Excel, Adobe Photoshop, Internet Explorer, Chrome, etc., are examples of computer programs. Computer programs are being used to develop graphics and special effects in movie making. Computer programs are being used to perform Ultrasounds, X-Rays, and other medical examinations. Computer programs are being used in our mobile phones for SMS, Chat, and voice communication. Computer Programmer Someone who can write computer programs or in other words, someone who can do computer programming is called a Computer Programmer. Based on computer programming language expertise, we can name a computer programmers as follows − C Programmer C++ Programmer Java Programmer Python Programmer PHP Programmer https://www.tutorialspoint.com/cgi-bin/printpage.cgi 2/63 i . e . , t o w r i t e c o m p u t e r p r o g r a m s

2017/8/26 Computer Programming Quick Guide Perl Programmer Ruby Programmer Algorithm From programming point of view, an algorithm is a step-by-step procedure to resolve any problem. An algorithm is an effective method expressed as a finite set of well-defined instructions. Thus, a computer programmer lists down all the steps required to resolve a problem before writing the actual code. Following is a simple example of an algorithm to find out the largest number from a given list of numbers − 1. Get a list of numbers L1, L2, L3....LN 2. Assume L1 is the largest, Largest = L1 3. Take next number Li from the list and do the following 4. If Largest is less than Li 5. Largest = Li 6. If Li is last number from the list then 7. Print value stored in Largest and come out 8. Else repeat same process starting from step 3 The above algorithm has been written in a crude way to help beginners understand the concept. You will come across more standardized ways of writing computer algorithms as you move on to advanced levels of computer programming. COMPUTER PROGRAMMING - BASICS We assume you are well aware of English Language, which is a well-known Human Interface Language. English has a predefined grammar, which needs to be followed to write English statements in a correct way. Likewise, most of the Human Interface Languages elements like verbs, nouns, adjectives, adverbs, propositions, and conjunctions, etc. are made of several Similar to Human Interface Languages, Computer Programming Languages are also made of several elements. We will take you through the basics of those elements and make you comfortable to use them in various programming languages. These basic elements include − Programming Environment Basic Syntax Data Types Variables Keywords Basic Operators Decision Making Loops Numbers Characters Arrays Strings https://www.tutorialspoint.com/cgi-bin/printpage.cgi 3/63 H i n d i , E n g l i s h , S p a n i s h , F r e n c h , e t c .

2017/8/26 Computer Programming Quick Guide Functions File I/O We will explain all these elements in subsequent chapters with examples using different programming languages. First, we will try to understand the meaning of all these terms in general and then, we will see how these terms can be used in different programming languages. This tutorial has been designed to give you an idea about the following most popular programming languages − C Programming Java Programming Python Programming A major part of the tutorial has been explained by taking C as programming language and then we have shown how similar concepts work in Java and Python. So after completion of this tutorial, you will be quite familiar with these popular programming languages. COMPUTER PROGRAMMING - ENVIRONMENT Though Environment Setup is not an element of any Programming Language, it is the first step to be followed before setting on to write a program. When we say Environment Setup, it simply implies a base on top of which we can do our programming. Thus, we need to have the required software setup, i.e., installation on our PC which will be used to write computer programs, compile, and execute them. For example, if you need to browse Internet, then you need the following setup on your machine − A working Internet connection to connect to the Internet A Web browser such as Internet Explorer, Chrome, Safari, etc. If you are a PC user, then you will recognize the following screenshot, which we have taken from the Internet Explorer while browsing tutorialspoint.com. https://www.tutorialspoint.com/cgi-bin/printpage.cgi 4/63

2017/8/26 Computer Programming Quick Guide Similarly, you will need the following setup to start with programming using any programming language. A text editor to create computer programs. A compiler to compile the programs into binary format. An interpreter to execute the programs directly. In case you don’t have sufficient exposure to computers, you will not be able to set up either of these software. So, we suggest you take the help from any technical person around you to set up the programming environment on your machine from where you can start. But for you, it is important to understand what these items are. Text Editor A text editor is a software that is used to write computer programs. Your Windows machine must have a Notepad, which can be used to type programs. You can launch it by following these steps − Start Icon → All Programs → Accessories → Notepad → Mouse Click on Notepad It will launch Notepad with the following window − https://www.tutorialspoint.com/cgi-bin/printpage.cgi 5/63

2017/8/26 Computer Programming Quick Guide You can use this software to type your computer program and save it in a file at any location. You can download and install other good editors like Notepad++, which is freely available. If you are a Mac user, then you will have TextEdit or you can install some other commercial editor like BBEdit to start with. Compiler? You write your computer program using your favorite programming language and save it in a text file called the program file. Now let us try to get a little more detail on how the computer understands a program written by you using a programming language. Actually, the computer cannot understand your program directly given in the text format, so we need to convert this program in a binary format, which can be understood by the computer. The conversion from text program to binary file is done by another software called Compiler and this process of conversion from text formatted program to binary format file is called program compilation. Finally, you can execute binary file to perform the programmed task. We are not going into the details of a compiler and the different phases of compilation. The following flow diagram gives an illustration of the process − https://www.tutorialspoint.com/cgi-bin/printpage.cgi 6/63

2017/8/26 Computer Programming Quick Guide So, if you are going to write your program in any such language, which needs compilation like C, C++, Java and Pascal, etc., then you will need to install their compilers before you start programming. Interpreter We just discussed about compilers and the compilation process. Compilers are required in case you are going to write your program in a programming language that needs to be compiled into binary format before its execution. There are other programming languages such as Python, PHP, and Perl, which do not need any compilation into binary format, rather an interpreter can be used to read such programs line by line and execute them directly without any further conversion. https://www.tutorialspoint.com/cgi-bin/printpage.cgi 7/63

2017/8/26 Computer Programming Quick Guide So, if you are going to write your programs in PHP, Python, Perl, Ruby, etc., then you will need to install their interpreters before you start programming. Online Compilation If you are not able to set up any editor, compiler, or interpreter on your machine, then tutorialspoint.com provides a facility to compile and run almost all the programs online with an ease of a single click. So do not worry and let’s proceed further to have a thrilling experience to become a computer programmer in simple and easy steps. COMPUTER PROGRAMMING - BASIC SYNTAX Let’s start with a little coding, which will really make you a computer programmer. We are going to write a single-line computer program to write Hello, World! on your screen. Let’s see how it can be written using different programming languages. Hello World Program in C Try the following example using our online compiler option available at www.compileonline.com. For most of the examples given in this tutorial, you will find a Try it option in our website code sections at the top right corner that will take you to the online compiler. Try to change the content inside printf, i.e., type anything in place of Hello World! and then check its result. It just prints whatever you keep inside the two double quotes. https://www.tutorialspoint.com/cgi-bin/printpage.cgi 8/63

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