COMPUTER: COMPUTER
SOFTWARE.
Machine Language
Machine language is the only language that
a compute understands directly without any translation, it is the
binary language. It is the language of 0's and 1's . It consists of
strings of binary numbers.
The binary codes are very difficult to memorize for
human beings that is why a machine language is cumbersome for a user.
Difference Between a High-Level Language and Low-Level Language
High-Level Languages
High-Level language are more suitable for human use than machine languages
and enable the programmer to write instructions easily using English
words and familiar mathematical symbols. These symbolic languages
are called High-Level languages. These high-level languages consist
of simple English sentences, which are very easy to understand and
memorize for human being.
Low-Level Languages
Both the machine and assembly languages are called Low-Level Languages.
An assembly language is one step higher than the machine language
in human readability. A machine language consists of totally of numbers
and is almost impossible for humans to read. In an assembly language,
some of these numbers are replaced by human readable symbols called
language for humans and almost of the same efficiency as machine language
for computer operations. An assembly language is a combination of
mnemonic operation codes and symbolic codes for address.
Assembly language is very difficult but it requires good skills for
programming. A program written in an assembly language is translated
into a machine language before computer can understand and execute
it. A computer program, which translates an assembly language program
into its equivalent machine language, is called assembler.
A program can be written in much shorter time and much precisely when
a high level language is used. A program written in a high level language
can be executed in any computer system, which has a compiler for that
programming language.
Operating System
Operating system provides link between the user and the computer.
It enables the user to have complete control over the computer system
by commands through the keyboard or any other input device. The
supervisor part of an operating system resides all the times in
the memory (RAM) of the computer after the computer is turned on.
An operating system performs the following tasks:
1. Controls basic Input and Output devices.
2. Allocates system resources.
3. Manages storage space
4. Supports application software
5. Maintains security
6. Detects equipment failure
This enables the user to achieve high efficiencies of which the
processing systems are capable. Operating systems can be classified
as:
1. Single User Operating System
2. Multi-User Operating System
Single User Operating System
Single user operating systems are used on individual systems or
Personal Computers. These operating systems reside on disks and
re called Disk Operating Systems (DOS). Some of the most widely
used single user operating systems are :
1. MS-DOS
2. PCDOS
3. OS/2
4. Windows 95
Multi-User Operating System
Multi-User Operating Systems are used for data processing on lrge
computer systems. They enhance the potential of computer systems
with multiprogramming, multiprocessing and timesharing facilities
making them suitable for large organizations. Some of the multi-user
operating systems are:
1. UNIX / XENIX
2. MACOSX
3. Windows NT
4. Windows 2000 Server
DOS
DOS stands for "Disk Operating System". It is a program,
which acts as an interface between the user and the computer hardware.
DOS allows manipulation of files and programs by interpreting and
processing the commands typed by the user.
The DOS software is automatically copied from a floppy disk or the
hard drive into the computer's memory whenever the computer is turned
on or booted(made a computer ready to be used by putting in its
instructions). DOS is not an application package that you start
and then exit when done. This is an operating system runs from the
moment you turn the computer on until you turn the machine off.
The major tasks the DOS must carry out are:
1. To control input and output devices.
2. To enable user to load and execute program.
3. To maintain an orderly system of data in the
disk.
Types of DOS Commands
There are two types of DOS Commands:
1. Internal Commands
2. External Commands
Internal Commands
Internal commands are a part of the DOS program COMMAND.COM and
are loaded into memory when you boot your computer. These commands
are needed to be used most often, although they are not seen when
we display the disk directory of filenames on our screen. Some internal
DOS commands are:
CLS
This command is used to clear the screen of a monitor.
Syntax: CLS
DIR
This command is used to display a list of current directly files
and subdirectories.
Syntax: DIR[drive:][path][filename][/p][1w]
CHDIR (CD)
This command is used to display the current directory or changes
in the current (default) directory.
Syntax: CD[drive:][path]
DEL
This command is used to deletes one or more specified files from
the disk.
Syntax: DEL[drive][path]file name[/p]
e.g. DEL Aslam.Doc
External Commands
External Commands are programs, which exist on the DOS disk or the
hard disk. They are run when you type their name on the command
line. For example, typing FORMAT at the DOS prompt results in a
program called FORMAT.COM being executed.
External Commands are not frequently used and DOS saves valuable
memory space by loading them only when required. Some the external
commands are:
CHKDSK
This command is used to checks the validity of a disk and reports
the total space, used and free space on the selected disk.
Syntax: CHKDSK [drive][path][/f][/v]
SYS
This command is used to create a bootable drive and installs the
main DOS files.
Syntax: SYS[drive:][path]drive2:
e.g. SYS A:
TREE
This command is used to display directory structure.
Syntax: TREE[drive:][path][/f][/a]
XCOPY
This commands is used to copy files (except hidden and system files)
and directories, including sub directories.
Syntax: XCOPY source [destination][/a|/m][/d:date][/p][/s][/e][/v][/w]
e.g. XCOPY *.*A:
DELTREE
This command is used to delete all files and sub directories in
a directory.
Syntax: DELTREE[/Y][pathname]
Booting the System
The term boot or bootstrap, when used with computers, means start
or startup. When we boot our computers, we are turning it on and
loading the Disk Operating System (DOS) into our computer's memory.
The sequence of events that occur between the time you turn on your
computer and the time it is ready for you to issue commands is referred
to as the boot process. At the completion of the boot up process
the system gives a DOS Prompt as soon as it is ready for operations. |
