Lec21&22.pptx programing language and there study

Programming Languages and
Their Comparative Study

Computer programming
• Computer Programming is defined as the process of creating computer
software using a programming Language. Computer programs are written by
Human individuals(Programmers)
• A computer program is a step by step set of instructions that a computer has
to work through in a logical sequence in order to carry out a particular task.
The computer executes these instructions (obeys the instructions) when told
to do so by the user.

Programming Languages
• Programming languages are the vocabulary and set of grammatical rules for
instructing a computer to perform specific tasks. There are many different types
of programming languages each having a unique set of keywords (words that it
understands) and a special syntax (grammar)for organising program instructions.
• There are many computer programming languages and so the programmer will
have to decide which one to use for solving a particular problem. These
languages must be learnt just as Swahili, English or French etc.

Syntax
• Syntax refers to the spelling and grammar of a programming language. Each
program defines its own syntactical rules that control which words the computer
understands, which combinations of words are meaningful, and what
punctuation is necessary. Text-based programming languages are based on
sequences of characters, while visual programming languages are based on the
spatial layout and connections between symbols (which may be textual or
graphical).

Syntax Example
• #include <studio>
• int main( void ) {
• printf( "Welcome to C!n" );
• return 0;
• }

Levels of programming languages
• Programming languages are classified into five major categories:
• Machine languages (first generation languages)
• Assembly languages (second generation languages)
• Third generation languages
• Fourth generation languages
• Natural languages.
• Machine and assembly languages are referred to as low level
languages; third generation, fourth generation and natural
languages are categorised as high level languages.

Low level vs high level language
• A low level language is machine dependent; that is, it is written to run on one
particular computer. A high level language is machine independent, which
means the high level language code can run on many different types of
computer.
• There are two types of low-level programming languages: Machine Language
and Assembly Language.

Lec21&22.pptx programing language and there study

Machine language – First Generation
Language (1GL)
• The machine language writes programs using the machine code of 1s and 0s,
which is directly understood by the computer. This makes the language suitable
for the understanding of the machine but very much more difficult to interpret
and learn by the human programmer.
• The main problems with using machine code directly are that it is very easy to
make a mistake, and very hard to find it once you realise the mistake has been
made.
• There was originally no compiler or assembler to process the instructions in 1GL.

Characteristics of 1GL
Advantages
• No translator is required
• The programs written in these languages utilize the memory in an efficient manner because it is possible
to keep track of each bit of data.
• Fastest to execute because it is already in the language that the computer can understand
Disadvantages
• Difficult to interpret (requires the aid of a reference manual to interpret the meaning of each code)
• Easy to make mistakes in the sequence of 1s and 0s; replacing a 1 for a 0 can result in the wrong
command/instruction being executed
• It is difficult to identify mistakes made
• Time-consuming and tedious to write
• Machine dependent
• Programming becomes more difficult as the complexity of the program increases

Assembly language – Second Generation
Language (2GL)
• Assembly language is written using mnemonic codes (abbreviated English
words) or short codes that suggest their meaning and are therefore easier to
remember.
• Assembly language contains human-readable notations that can be further
converted to machine language using an assembler(converts assembly level
instructions to machine level instructions.)
• These codes represent operations, addresses that relate to main memory,
and storage registers of the computer. Typical codes might be: LDA, STO, ADD,
NOP, etc.
• Assembly language are a necessary bridge between the underlying hardware
of a computer and the higher-level programming languages—such as Python or
JavaScript—in which modern software programs are written.

Example
An example of a program code to add and store two
numbers would be:
• LDA A, 20 : load accumulator A with the value 20
• ADD A, 10 : add the value 10 to accumulator A
• STO B, A : store contents of accumulator A into
storage register B
• NOP: no operation (stop here)
• An accumulator is a type of register included in a CPU

Characteristics of 2GL
• As with machine language, assembly language is machine dependent.
• Assembly language, being machine dependent, is faster and more
efficient in the use of hardware than high-level programming
languages.
• Assembly languages have to be translated into machine language by
language translators known as assemblers for the processor to
understand.
• Easier to write than machine language
• The code is not very easy to understand, hence the introduction of
high level programming languages.

Assemblers and Compilers
• Assemblers and Compilers are programs that convert high level
languages into machine code.
• The assembly-language program must be translated into
machine code by a separate program called an assembler. The
assembler program recognises the character strings that make
up the symbolic names of the various machine operations, and
substitutes the required machine code for each instruction.
• A Compiler is a program that converts the entire source
code(compiles it) into machine language at one time before the
computer can run the program at a later time. While compiling
the source code into machine code, it checks that the syntax is
properly written by the programmer for the programmer to
debug the program.

Interpreters
• The interpreters are programs that translates the high level
program code one statement at a time, that is, it reads a code
statement, converts it to one or more machine language
instructions, and then executes the instruction before moving
translating the next code statement in the program. If there is
any error in the statement, the programmer can correct the
error before the interpreter evaluates the next statement.
• Interpreters are slower than Compilers because interpreters
convert a statement at a time and runs it before moving to the
next line.

High-level programming languages
High level programming language is defined as one that is
machine independent and uses variables and objects, Boolean
expressions, functions, loops, arrays, threads, locks which are
similar to their meaning (abstraction).
• High-level languages have evolved over the years and can be
grouped into categories: Third Generation Languages (3GL),
Fourth Generation Languages (4GL), Object Oriented
Programming Languages (OOP), Fifth Generation Languages
(5GL) and Scripting Languages

High-level programming languages
• These languages are problem oriented, so they are machine
independent.
• Since high-level languages reflect the logic and procedures
used in a human algorithm, the programmer is able to
concentrate on developing task algorithms rather than on
how the computer will carry out the instructions.
• the programmer must still specify a complete set of detailed
instructions. The words and grammar of high-level
languages are English-like and this makes the programs
more readable and easy to write.

Characteristics
• A high-level language is governed by a strict syntax (set of grammatical
rules).
• they are easier to read, write, and maintain.
• They also permit faster development of large programs.
• programs written in a high-level language must be translated into
machine language by a compiler or interpreter.
• They are machine independent hence portable
• They are user friendly and easy to learn
• They are more flexible hence they enhance the creativity of the
programmer, increasing productivity
• They are executed much slower than low-level programming languages

Third generation languages
• The third generation is also called procedural language /3 GL. It consists of the use of a
series of English-like words that humans can understand easily, to write instructions. Its
also called High-Level Programming Language. For execution, a program in this
language needs to be translated into machine language using Compiler/ Interpreter.
Examples of this type of language are C, PASCAL, FORTRAN, COBOL, etc.
• Advantages of third generation programming language
• It is easy to develop, learn and understand the program.
• As the program written in these languages are less prone to errors they
are easy to maintain.
• The program written in these languages can be developed in very less
time as compared to the first and second generation language
• Same code can be copied to another machine & executed on that
machine by using compiler-specific to that machine

Third generation languages
Disadvantages :
1. Compiler/ interpreter is needed.
2. Different compilers are needed for different machines.

Fourth Generation languages
The fourth-generation language is also called a non – procedural language/ 4GL. It enables
users to access the database. Examples: SQL, FoxPro, Focus, etc. The fourth generation
programming languages were designed and developed to reduce the time, cost and effort
needed to develop different types of software applications. These languages are also
human-friendly to understand.
Advantages :
1. Easy to understand & learn.
2. Less time required for application creation.
3. It is less prone to errors.
Disadvantages :
1. Memory consumption is high.
2. Has poor control over Hardware.
3. Less flexible.

Fifth generation languages
• The fifth-generation languages are also called 5GL. It is based on the concept of artificial
intelligence. It uses the concept that that rather than solving a problem algorithmically, an
application can be built to solve it based on some constraints, i.e., we make computers
learn to solve any problem. Parallel Processing & superconductors are used for this type
of language to make real artificial intelligence.
• Example: PROLOG, LISP, etc.
Advantages :
1. Machines can make decisions.
2. Programmer effort reduces to solve a problem.
3. Easier than 3GL or 4GL to learn and use.
Disadvantages :
1. Complex and long code.
2. More resources are required & they are expensive too.

Major high level programming languages used
• FORTRAN (FORmula TRAnslator)developed in the late 1950s
developed to design scientific applications
• COBOL (Common Business Oriented Language) developed in
early 1960s to develop business applications.
• RPG (Report Program generator) was developed in early
1960s to assist in generating reports and complex
calculations.

• BASIC (Beginner’s All-purpose symbolic instruction code)
developed in mid 1960 Basic versions include MS-BASIC,
QBASIC, SmallBASIC and visual basic.
• Pascal was developed in the late 1960s for the purpose of
teaching structured programming concepts
• C developed in the early 1970s to write system software
• Ada was developed in the late 1970s originally developed to
meet the needs of embedded computer systems

• C++ developed in the 1980s is an object-oriented language
mainly to develop application software
• Note that in addition to the major languages discussed above,
there are many other programming languages that have been
developed such as JavaScript, and Python

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