What happens when the computer turns on?
Regardless of which PC you turn on, you will see that some text is missing on the black screen. Your operating system can be DOS, Windows 3.x, Windows 9x, NT, Windows 2000, Unix or Linux. You will see these articles in all of them. The operating system is then activated automatically or with a command you type on the black screen.
So what are these lines that came into effect before the operating system?
We've talked about the BIOS before. Bios, which means Basic Input / Output System, is actually a small software installed on a chip on the motherboard. This software takes the first steps for the hardware to be recognized by other components and the operating system, tests if some hardware is working properly when the system is turned on, and allows certain features to be set. Here you can understand from these articles that appear on the black screen when you turn on your PC, these first actions that the BIOS performs to turn on your system. These processes are called POST - Power On Self Testing / Automatic boot tests when these articles are displayed on the screen.
Every time you turn on the computer, the POST procedure (routine) in the BIOS checks the basic resources of your PC: Does the memory work? Do the input / output units stay in place? Is the operating system where it should be? Relation is established with the peripherals and communication ports. If everything is going well, there is no problem. But if there is a problem in any unit, the testing process is stopped, the sad news is reported to us on the screen ...
This test process, which can be viewed on the screen of the PC, mostly focuses on RAM memory; The more main memory, the longer POST will take. The main addresses of the basic input / output programs are transferred to the RAM, so that the application software we will use is also allowed to use the input / output units in non-standard ways. a.)
As you can see, many processes are performed at system startup, and as the hardware and software installed on your system change, the boot time may change depending on the motherboard's features and your BIOS settings. Most users tend to evaluate their system performance with this boot time. However, as can be seen, this time can be very variable due to the hardware and software installed at boot, so the performance of the PC is not measured by the boot time.
Note: 1. If the texts scroll on the screen the first time you turn on your system and you have difficulty reading the information you are looking for, you can stop the scrolling text by pressing the Pause button on your keyboard. Operations will continue when you press enter.
2. If you are sure that the hardware on your system is working properly, you can speed up the boot of your system by canceling some POST operations from BIOS Setup. When you set “Quik Power On Self Test” option to “Enabled” in BIOS Features Setup section, the memory counting process at boot will be canceled and your system will boot faster.
General Structure of Operating Systems
The BIOS is not exactly an operating system; acts as a bridge between the hardware and the operating system. Electronic circuits, CD drives, processor, graphics card ... the hardware we pay for is half the computer! In the introduction, we mentioned that the other tomorrow was called software. The computer is a general-purpose device, so general-purpose that it has no defined function and task when you ask: "It does what it does". The task of the software is to activate the body that just rests on your desk (or knee) and to give the functions defined in this general purpose device. The software has one more function. It is easy to use an extremely complex device, to create a bridge between you and electronic circuits. The user does not interfere with the internal functioning of the computer, but can manipulate it. This orientation is possible with application software and system software that enable them to work if we descend from the top of the pyramid to the bottom. The most important of the software collected under the heading "system software" is the operating system. The operating system represents the operation of all the complex hardware units we have described so far with some commands or images and icons. You can also use your PC without knowing the basic operating principles of processor, BIOS or memory, but you cannot master your computer without knowing the operating system. If you are going to use DOS, you won't know DOS, if you have Windows, if you have Unix or Linux, or if you have a Mac, MacOS!
This is the reason why software developers are trying to develop operating systems and graphical user interfaces that are increasingly used ... Thanks to system software such as DOS, Windows, OS / 2, Linux, what's happening on your hard disk, how the CD-ROM works and how the processor works you don't have to know what you did. You are expected to know only a few commands or click the icons on your screen with the mouse.
An operating system is a comprehensive program that determines how the computer handles its basic functions (receiving, processing, displaying, writing or sending data via the telephone line, etc.). The operating system undertakes resource management and coordination for the efficient use of computer resources. No matter how it is stored in any environment, no matter how it is installed, all operating systems fulfill this task.
DOS Operating System
We will start with the operating system used in PC (Personal Computer) from the old operating systems, MS-DOS that still stands on one side of our Windows PCs, even though most users no longer use it directly. We will also consider some operating system concepts while explaining DOS. So it's a good idea to take a look at DOS pages even if you don't use DOS.
The part of DOS that gives the user the ability to control the system in different ways is called the "User Command Processor". DOS also includes a set of functions and special commands for different components of the machine and input / output units. Some of these commands and functions can be used directly by users, and some are used by application software. Some are also by everyone.
Let's say you wrote a post and you're saving it to disk. The word processor (the program in which you write the text) does not do the job directly about the disk, it just uses the disk-related functions of the operating system. Therefore, changing this function in DOS in any way directly affects all software. Some software bypass the operating system and access the hardware components directly.
DOS operating system installed on your PC consists of the following modules:
ROM-BIOS: Basic input-output system stored in ROM (read-only memory).
OPENING RECORD: A small and simple recording on the disk that allows the computer to perform "bootstrap". This recording is not permanent, that is, it does not stop in RAM while your PC is running.
· IO.SYS and MSDOS.SYS (or IBMBIO.COM and IBMDOS.COM): System files of DOS. These files, which can be seen as attachments of programs in the ROM-BIOS, include programs that perform additional operations related to peripherals. These files located in the main directory of your disk are hidden, so you cannot see them with the DIR command.
COMMAND.COM: The main function of the system program included in this file is to interpret and execute the commands we use while working on DOS. COMMAND.COM is located on disk, it is not a hidden file, meaning it appears with the DIR command.
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If your COMMAND.COM stored in main memory while the machine is running is deleted or corrupted, your PC will not boot ...
Attention: As a user, you are not allowed to do anything with these system files. Just conceptually, you just need to know what these files do. Just in case, if you take a backup of these system files, you will be very good ...
CONFIG.SYS FILE: It is the file that is loaded at boot to introduce system related files and hardware parts that can be used by the computer. The file is called with any word processor and the necessary changes can be made by the user.
AUTOEXEC.BAT FILE: Programs and commands that are wanted to run after the operating system is installed are included in this file. The file is called with any word processor and the necessary changes can be made by the user.
Installing DOS Operating System On Boot
ROM memory is tested and read when the computer is turned on for the first time. Then RAM memory is tested, if a problem occurs, it sends a message to the screen and does not go into operation.
After the memory test, A checks the floppy drive and, if no floppy disk is installed, it does the job of loading the operating system from disk C and loads the hidden files IO.SYS and MSDOS.SYS, which enable recognition of existing devices.
The configuration file, CONFIG.SYS, is loaded. It then loads the COMMAND.COM file and the AUTOEXEC.BAT file. The computer turns on and C: \> will appear on the screen. DOS commands can be applied after that.
If a floppy disk is inserted when testing drive A and DOS operating system files are available, they open from drive A and write A: \> to the screen.
If the DOS operating system is not installed on the floppy disk in drive A, it will display the following message.
Non-System Disk Error
Replace and press any key when ready
After this message, a non-system disk in drive A is removed; Either a key is pressed and the computer is turned on from the C drive, or the floppy disk installed with the DOS operating system is inserted and the computer is turned on from the A drive by pressing a key.
The computer does not boot from C drive: DOS operating system may not be installed. The files of the DOS operating system may be corrupt and need to be reinstalled, or the disk may be corrupt.
If the AUTOEXEC.BAT file is not found on the floppy disk in drive C or drive A when turning on the computer, the date and time information is displayed on the screen and these lines are passed by pressing the ENTER button and the computer is turned on.
Drive Replacement
To enter A drive while in C drive, A: is written and press enter.
To enter A drive while in A drive, type C: and enter button is pressed.
Naming Files
In DOS operating system, the files are given at least 1 character, maximum 8 characters name and 3 characters in extension. Files may not be named as extensions, but there are some cases where it is absolutely necessary to name them. A period (.) Character must be placed between the file name and its extension. No spaces are used in the filename and extension.
The file extension gives us information about that file. The meaning of some file extensions is as follows:
EXE: Programs with this extension run directly.
COM: They work directly in these programs.
BAT: Programs that contain DOS commands for batch operations.
SYS: System file in DOS operating system.
TXT: File containing text.
DAT: File containing data.
HLP: File with explanations about the subject, help information.
* and? characters are contained in the DOS commands, in the file or extension name. When used as wildcards:
1. * character, 1 to 8 characters in the filename; If it is used in the file extension, it represents 1 to 3 characters and gives meaning regardless.
2nd. ? character represents a single character in its position and gives meaning regardless.
DOS Commands 1. Internal (Internal) Commands
These are commands that settle in RAM when the computer is turned on. The RAM is deleted from memory when the computer is turned off. The computer loads the RAM into memory when it is turned on again.
2. External (External) Commands
For these commands to work, files must be present on the computer's disk or floppy disk.
Most Used DOS Command: DIR
DIR, which is the first learned and most used command, provides listing or searching of files in the directory or below the desired drive.
The usage form and parameters of the DIR command are as follows (In addition to these parameters, the parameters used with DubleSpace are also available.):
DIR [drive letter:] [\ directory name] [\ file name] [/ P] [/ W] [/ A [[:] assignments]] [/ O [[:] sorting]] [/ S] [/ B] [/ L] [/ C [H]]
· / P Displays page by page. On the screen, we can see relevant details such as filename, file capacity, date and time the file was processed. If the files to be listed are too many to fit on one screen, when the screen is full; we press a key to see a list of other files.
· / W Lists only directory and filenames with 5 names per line.
· / A Lists by file assignments. Assignments:
D Directories (directory)
R Only read-only files
o Hidden files
o A Files that need to be archived
/ O Sort by:
o By N Name (alphabetically).
o S According to file size.
o By extension (surname) E (alphabetically.
D By date and time.
o G Directories
· / S File or directory search, listing with subdirectories.
· / B List only names and extensions without a header
· / L List in lowercase.
If the drive name and directory are not specified, the active (current) drive and directory are accepted as the current drive and directory name.
Examples:
C: \> dir c: \ windows \ command \ *. Com
Finds and lists files with extension com, regardless of the name in the subdirectory named command in the windows directory on the C drive. If not, it displays the message File Not Found on the screen.
C: \> DIR KEYBTK.COM/S
It searches which directory the keybtk.com file located in all directories and subdirectories on the C drive.
C: \> DIR * .EXE / S / P
Searches for files with extension EXE and lists page by page regardless of the name in all directories and subdirectories on drive C.
C: \> DIR A:
Displays files on floppy disk that are inserted into drive A while on drive C. If there is no floppy disk, it will write the message stating that it cannot read the floppy disk:
Not Ready Error Reading Drive A
Abort, Retry, Fail
Abort: Select the initial letter A and abandon the process and return to the DOS command line.
Retry: If we answer with the initial letter R, we insert the floppy disk. We ensure that the command we have given is executed.
Fail: If we reply with the letter F, it will be returned to the DOS command line.
Format Command
It is the making (formatting) of a floppy disk or disk on the computer. Used diskettes or disks can be reformatted. However, the information contained in it is deleted. Care should be taken when using the Format command so that the information is not accidentally deleted. Usage form:
Format / q / u / s / f: size
Q: Fast formatting.
U: Performs full formatting and does not allow unformat command to run to recover deleted information.
Q: Formats the floppy disk as a "system floppy", it copies two hidden files, IO.SYS, MSDOS.SYS files, and COMMAND.COM to the floppy or disc.
F: Determines the size of the floppy. Valid sizes are 720 KB, 1.2 MB, 1.44 MB.
C: \> FORMAT A: / S
Formats the floppy disk in drive A and loads system files. The computer can be turned on with this floppy disk. Because of formatting the floppy in this way, a certain part of the floppy is used.
MD (Make Directory-Indexing) Command
A directory is created to keep related files together. Directory name must be 8 characters or less. The MD command is used to create a new directory. Examples :
C: \> md faculty
The directory named faculty is created on the C drive.
C: \> md faculty \ department
It creates a partition directory within the faculty directory on the C drive.
C: \> md a: \ account
Creates the account directory on drive A.
CD (Change Directory-Directory Change) Command
It is used to enter the directory or move to another directory.
CD ..: Moves to a higher directory.
CD \: Returns to the home directory.
Copies all the files in the COBOL directory on drive C to the BACKUP directory on drive A.
C: \ DBASE> COPY * .EXE C: \ DATA
Copies files with extension EXE from the DBASE directory on drive C to DATA on drive C.
Other DOS Commands ATTRIB Shows and modifies file assignments.
BACKUP Backs up files to floppy disks
CHKDSK Gives information about hard disks and floppy disks, checks and repairs corruption
CLS Deletes the screen.
DATE Shows and modifies the date.
DEFRAG Corrects, organizes and speeds up file fragmentation on the disk.
DEL Used to delete files. Care should be taken when using this command.
DELTREE Deletes directories with files and subdirectories.
DISKCOPY Copies one floppy disk to another.
DOSKEY simplifies operations on the DOS command line.
DOSSHELL DOS allows you to perform operations on the command line from the menus.
EDIT is an editor for writing and editing.
EMM386 supports Expanded memory.
Provides summary information about FASTHELP MSDOS commands.
FDISK It is used to create hard disk partitions.
FIND Searches for a string in the files and displays the lines it finds.
Help system that provides information about HELP DOS commands.
INTERLNK It is used to connect two computers through parallel or serial ports. Contacted
INTERSRV INTERLNK on one computer and INTERSRV on the other
KEYB is used to organize the keyboard according to a language.
LABEL Gives the disc a label or changes it.
LH Loads a program into the upper memory.
LOADHIGH Loads a program into the upper memory.
It reports on MEM Memory.
MORE Displays what is displayed on the page page by page.
MOVE Moves files from one place to another, changing directory names.
MSAV Virus scans.
MSBACKUP Used to backup and restore.
Gives technical information about MSD Computer.
PATH Defines the search path for executable files, and shows the defined ones.
Changes the PROMPT DOS command line prompt. PROMPT $ P $ G
QBASIC is used for writing programs in Quick BASIC language.
REN Changes the name of the files.
Restores backups taken to floppy disks with RESTORE BACKUP.
Shows, creates, modifies or deletes SET DOS environment variables.
SETVER Used to run programs in different MS-DOS versions
SYS installs DOS system files on a floppy disk or hard disk.
TIME Shows and changes the time.
TREE lists directories graphically.
TYPE Displays the content of a text file.
Returns files deleted with UNDELETE DEL. Use immediately after deletion
UNFORMAT Returns a formatted disk. Use immediately after formatting.
VER Returns the version of the currently running MS-DOS.
Returns the label and serial number of the VOL Disk.
VSAFE stays in memory as TSR and detects viruses.
XCOPY Copies files and directories with their subdirectories when requested.