Python 1.1 - All about programming world


Before diving directly into python, let’s first understand some concepts about what are programs, why do we write programs, what is a programming language, why do we need it and all the basic concepts about programming world. No matter what programming language you are learning, you must know these things too. These topics can also be asked in job interviews, written exams, viva etc. You are now going to learn a programming language, then as a programmer you must know these basic topics too. So let’s start. 

All about programming world

We all use popular apps like Google, YouTube, Elyments, Facebook, Instagram, Twitter and millions of other applications. Have you ever thought about how these applications are made? Let me tell you that all these applications are made by writing programs. And to write programs, we need a programming language. So a programming language helps programmers to write programs. Programs can be created for computers, smartphones, tablets and for all the devices that have a processor and memory. Why processor and memory? Because programs are executed by a processor and the processor uses memory to store program’s data. When we say memory, it means we are talking about RAM because a processor can only access RAM. RAM stands for ‘random access memory’ which means a CPU (processor) randomly accesses the RAM to store and retrieve the data. So some examples of programming languages are C, C++, JAVA, Python etc. By using these languages, we can write programs to create applications. So programs are first written by programmers to create applications. These programs are then executed by the processor or CPU (Central processing Unit). Then finally the processor gives us the result. To achieve this result, a programmer writes programs.   

Question – Why do you need to learn programming language?

Answer – The present era is digital age where everything happens on computer and mobile. Everybody in the world wants to earn money to lead a life. For this, people do different jobs. One of those jobs, is that of a programmer or developer. A programming job is a job that the world always needs. A programming job is such a job that has never taken off till date. This world needed programmers and always be. You can say about programmers that “Sky is not the limit”. I think this explanation is enough for you that why should you learn programming.       

Important Note: You (User) will write programs and give those programs to a processor so that the processor can execute them and give you the final result. The programs you will write are called source code. The source code will be in English language. But the problem is, processor doesn’t understand English. A processor understands only machine code since processor is a machine. Therefore, first we have to convert the source code into machine code so that it can be executed by processor. In addition to source code and machine code, there are many other forms of a code such as Object code, Byte code etc. But the processor cannot execute these forms either. Keep in mind that, processor can understand only and only machine code and not any other code. We will understand all the forms of a code in upcoming topics in detail. For now, observe the following image.




Now we know that a processor can execute only machine code. Let’s understand some other important terms and the other forms of a code -

Program

A program is a set of instructions/statements or commands that is created by a programmer to get the machine (computer) or any other electronic or digital device to do some work. Remember that the device must have a processor so that our programs can be executed. Programs are always written in a programming language (low level or high level language). We will write programs in a high level language (python).

Programming language

So you want to write programs for a machine? Have you thought about where and how to write programs? Here comes the programming language. A programming language is used to write programs. It provides an environment for programmers to write programs easily. By using programming language, a programmer can write programs in English language. Also, a programming language knows how to communicate with computer (processor). There are two types of programming languages – low level programming language and high level programming language which we’ll cover later.   

Source code

The code/program written by a programmer is called source code. It is generally written in a high level language (Because nowadays low level language is used with little to no). A source code is written in plain text using a human readable language such as English. For example, if you have written a program in python and saved the file named “sample.py” then this file will be called Source code since it is written by programmer himself with a high level language.

Object code

If you come from C/C++ background, then you would know what an object code is. And if you are not from C/C++, then just read and move on to the next topic. We get the object code after compiling (compiling means executing the program) a C or C++ program. So a C/C++ compiler generates object code. An object code is a file that has an extension “.o” or “.obj”. Object code is often called machine code but it is not a complete machine code. The processor cannot execute an object code so the object code is converted into machine code (.exe file in Windows OS) by a program called Linker. Since object code is the first step to become a machine code, hence it is also called a machine code. But again Object code is slightly different from machine code.

Note: In C/C++, we get the ‘.exe’ file in only windows machine (Windows OS). When a C/C++ source code is compiled in another machine such as Linux and Macintosh then we don’t get an ‘exe’ file (because Linux and Mac do not understand ‘exe’ files) instead we get a file which can be executed by Linux and Mac OS. Such file doesn’t have any specific extension. So the thing is, C and C++ programming languages are also machine independent and portable but the code (.exe file in windows OS and other files in Linux and Mac OS) which is generated by compiler is machine dependent. 

Let’s clear your doubt by taking an example. Suppose you are a developer and you created a program in C/C++ language for a customer. Let’s assume that you used Windows OS to develop the program so at the end you will get an ‘exe’ file since Linker will generate ‘exe’ file in Windows machine. This ‘exe’ file can only be run on Windows machine and not on Linux, Mac or other machine. In order to run the file on Linux and Mac, you have to compile the source code again in Linux and Mac so that C/C++ could generate the compatible files for these operating systems. The conclusion is that you have to compile the source code every time for different machine in C/C++ languages.      

Machine code

A Processor cannot execute the source code, object code or any other code. It can only understand and execute the machine code. Machine code is the code that is directly executed by a processor. A machine code contains only 0s and 1s since computers work only with 0s and 1s (binary language). So machine code is also called binary code or binary language. It does not matter in which high level language (C, C++, Python, Java etc.) we are creating the program, at the end, the machine code will be generated and executed by the processor so we can get the output/result.

Note: We (programmers) will write the source code (Source code is in English language), but the processor cannot execute the source code because a processor can understand only and only machine code (Machine code is in the language of 0s and 1s). So the source code will be converted into machine code. In this process of conversion, there may be other forms of code such as Object code in C/C++ programming. In C/C++ language we get the object code before the machine code. Another form of code is Byte code that we will get before machine code in Python programming language.

If you have no C/C++ background, then you may have some difficulty to understand object code but don’t worry about it and move on.

Byte code

As we have understood that when a C/C++ source code is compiled then we get the object code, and then the object code is converted into machine code by Linker. Here compiling means executing or running the source code. When a Python source code is compiled then we get an intermediate code called Byte code. Python does not generate object code. Byte code is a file that will be produced by Python Compiler and then the Byte code will be executed by Interpreter (PVM) to generate the machine code so processor could execute it. We will understand compiler, interpreter and PVM very shortly. Since each instruction is of one Byte in Byte code, hence it is called the Byte code. The advantage of the Byte code is that the Byte code is machine independent which means that the Byte code can be executed on any Machine in the world, no matter if the machine is running on Windows, Linux/Unix or Mac. We don’t need to compile the Python source code every time for different machine. We just need the Byte code. This is not possible with the object code in C/C++. So the final code generated by C/C++ is machine dependent (.exe file for windows OS) since ‘.exe’ files generally run on Windows OS and code generated by Python compiler (Byte code) is machine independent. 

Note: In order to execute the Byte code on any machine in the world, we just need a program/software named PVM on that machine. Let’s clearly understand this concept through an image – 



Everything clear? As we can see the difference between a C code and a Python code. We will discuss about PVM soon.

Till now we understood that we will write source code but a machine/computer cannot understand it, it only understands machine code so there must be a way to convert a source code into a machine code. And this task is done by “Language translator”.

Translator

We cannot convert the source code into machine code by ourselves. This work can only be done by a software. That software is called a translator. So a programming language translator is a software/program that converts a source code into machine code. There are 3 types of language translators exist – Compiler, Assembler and Interpreter. Different programming languages use different translators with their benefits and drawbacks. Some programming languages use a mixture. For example, Python uses mixture of Compiler and Interpreter both. When you use any programming language then you don’t need to exclusively use/download a translator, it comes with that language.

So far we have discussed about concepts of programming language. Now let’s talk about types of programming languages –




As you can see there are many drawbacks of using a low level language, that is why the world uses high level language to create applications. But it does not mean that low level languages are not used at all. Assembly language is used to develop hardware related applications such as device drivers and high level languages are used to develop user friendly applications.

As you know that source code cannot directly be executed by computer so first we need to convert it into machine code so that computer(processor) can execute it and give the final result. And to convert the source code, we have three “Translators” that will do this task.

Comments

Post a Comment

Popular posts from this blog

Python 4.4 - Points to remember

  Points to remember ·          Operators are symbols used to perform some operations on operands. For example, in statement z=x+y, ‘+’ and ‘=’ are operators and ‘x’, ‘y’ and ‘z’ are operands. Addition operator is used here to add two operands ‘x’ and ‘y’ and assignment ‘=’ operator is used to assign the result of addition to operand ‘z’. ·          Operators which operate upon single operand are called Unary operators such as unary ‘+’ and unary ‘-’. For example, -5, -6.8 ·          Operators which operate upon two operands are called Binary operators such as addition, subtraction etc. For example, 5+7, 45-23, x+y, x/y ·          Arithmetic operators perform mathematical calculations such as addition, subtraction, multiplication, division. Modulus, floor division and exponentiation. ·          Assignment operator ‘=’ is used to assign a value to the left side variable. ·          There are compound assignment operators such as ‘+=’, ‘-=’, ‘*=’, ‘/=’, ‘//=’, ‘%=’ and ‘**=’
Read more

Python 3.6 - Points to remember

  Points to remember ·          A variable is any location in the computer’s memory which holds a value. ·          Python is memory efficient when dealing with variables as compared to other programming languages. ·          An identifier is a name given to a variable, function, class, list, tuple etc. Identifiers are used to identify things in Python. ·          Keywords are reserved words in Python that have some special meaning and they can only be used for pre-defined purpose. ·          Comments are always used to describe the features of a program and ignored by Python compiler and interpreter. ·          ‘#’ symbol is used to create a single line comment.    ·          Python does not recommend Triple double quotes (“””) or triple single quotes (‘’’) as multi line comment. ·          If triple double quotes (“””) or triple single quotes (‘’’) are written as the first statement of a class, function, module etc., then they are called Docstrings and can be used t
Read more

Python 3.3 - Datatypes in Python

Image
  Datatypes in Python As we have already discussed that data type refers to the type of data. So datatype implies that what type of data we can store in our Python program. There are two categories of datatypes available in Python – Built-in data types and User defined data types Built-in data types The data types which are pre-defined in Python are called built-in data types. These data types have already been developed by Python developer team which we can use directly. So we do not need to do anything in it. Following are built-in data types – ·          None ·          Numbers ·          Boolean ·          Sequences ·          Sets ·          Dictionary   These datatypes are further classified in some more datatypes. Observe the image below – 1.    The None Type The None Type represents no value. When we have no value to store in a variable or object then we can store None into that variable. There might be a case when we will need a value in a variable late
Read more