computer languages

1. Computer Languages
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2. Types of Programming Languages
• Machine Languages
• Assembly Languages
• High Level Languages
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3. Machine Languages
• A machine language consists of the numeric codes for the operations that a
particular computer can execute directly.
• The codes are strings of 0s and 1s, or binary digits (“bits”), which are
frequently converted both from and to hexadecimal (base 16) for human
viewing and modification.
• Machine language instructions typically use some bits to represent
operations, such as addition, and some to represent operands, or perhaps
the location of the next instruction.
• Machine language is difficult to read and write, since it does not resemble
conventional mathematical notation or human language, and its codes vary
from computer to computer.
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4. Assembly language
• Assembly language is one level above machine language.
• It uses short mnemonic codes for instructions and allows the programmer to introduce
names for blocks of memory that hold data.
• One might thus write “add pay, total” instead of “0110101100101000” for an instruction
that adds two numbers.
• Assembly language is designed to be easily translated into machine language.
• Although blocks of data may be referred to by name instead of by their machine
addresses, assembly language does not provide more sophisticated means of organizing
complex information.
• Like machine language, assembly language requires detailed knowledge of
internal computer architecture.
• It is useful when such details are important, as in programming a computer to interact
with peripheral devices (printers, scanners, storage devices, and so forth).
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5. High Level Languages
• A high-level language (HLL) is a programming language such as C,
FORTRAN, or Pascal that enables a programmer to write programs
that are more or less independent of a particular type of computer.
• Such languages are considered high-level because they are closer to
human languages and further from machine languages.
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6. Assembler
• An assembler translates assembly language programs into machine
code.
• The output of an assembler is called an object file, which contains a
combination of machine instructions as well as the data required to
place these instructions in memory.
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7. Linker
• Linker is a computer program that links and merges various object
files together in order to make an executable file.
• All these files might have been compiled by separate assemblers.
• The major task of a linker is to search and locate referenced
module/routines in a program and to determine the memory location
where these codes will be loaded, making the program instruction to
have absolute references.
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8. Loader
• Loader is a part of operating system and is responsible for loading
executable files into memory and execute them.
• It calculates the size of a program (instructions and data) and creates
memory space for it.
• It initializes various registers to initiate execution.
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9. Interpreter
• An interpreter translates high-level language into low-level machine
language.
• An interpreter reads a statement from the input, converts it to an
intermediate code, executes it, then takes the next statement in
sequence.
• If an error occurs, an interpreter stops execution and reports it.
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10. Compiler
• Compiler, translates high-level language into low-level machine
language.
• A compiler reads the whole source code at once, creates tokens,
checks semantics, generates intermediate code, executes the whole
program and may involve many passes.
• Compiler reads the whole program even if it encounters several
errors.
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11. • User writes a program in C language (high-level language).
• The C compiler, compiles the program and translates it to assembly
program (low-level language).
• An assembler then translates the assembly program into machine code
(object).
• A linker tool is used to link all the parts of the program together for
execution (executable machine code).
• A loader loads all of them into memory and then the program is executed.
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