Subject 1: General Computer Calculations
Booting: The process of reading a system program from disk into main memory and putting the computer into a usable state is called booting.
Data Representation and Operations
Fractional Number-System Conversion
First fractional place of an octal number = 1/8 = 0.125 Second fractional place of an octal number = 1/8 X 1/8 = 0.015625 0.1875 = ‘1’ X 0.125 + ‘4’ X 0.015625 = 0.125 + 0.0625
- Left shift: Moves one bit at a time to the left, filling the remaining part on the right with 0s - Left rotate: Moves one bit at a time to the left, while the numbers that were on the left move unchanged to the right end
- Time Division Multiplexor -> A time division multiplexor can only be used with synchronous data multiplexing
- Complement:
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In the case of binary numbers -> 1’s complement: Change 0s and 1s to each other -> 2’s complement: 1’s complement + 1
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In the case of decimal numbers -> 9’s complement: A value that can be added to each digit to make 9 550+x=999 x=999-550 x=449
-> 10’s complement: A value that can be added to each digit to make 10
Note) If a carry occurs and 10 is formed, 1 is also added to the preceding digit, so take this into consideration
cf)
- Subtraction using complements https://wpaud16.tistory.com/115
- A control word (Word) indicating the status of a system related to a program (Program) PSW - Program Status Word tip) When you see “word,” think psword
Full adder: 2 half adders + 1 OR (logical sum) gate -> 3 inputs, 2 outputs
Storage Devices
Magnetic tape load point: The position where the head is placed when performing input/output operations on magnetic tape EOT: End Of Tape, ending position BOT: Beginning Of Tape, starting position
- Blocking factor: Number of RECORDs in one block
Magnetic disk
- Track
- Sector
- Cylinder
tip) In a magnetic disk, the number of tracks and the number of cylinders are the same.
Character Data Representation Methods
1. Internal
2. External: -ASCII: 7 (data bits) + 1 (parity bit) 1 start bit, 2 stop bits, 1 parity bit, and 7 data bits Adding them all gives 11, 110 bps divided by 11 = 10 characters
Subject 2: Package Utilization
Spreadsheet, Excel
- The data of each individual student, which is a set of related fields in a table and serves as the basic unit of data processing -> The basic unit is called a cell, but each individual set of recorded data is called a record.
- ROUND function: Rounding - MOD function: Remainder of division
Subject 3: PC Operating Systems
Loader (patch, Fetch, loader)
: If it says bringing something into main memory (or the CPU), choose this!
- Loader functions: Allocation, linking, relocation
Windows 98
- Alt + F4: Close window (terminate program) / Shut down Windows - Ctrl + ESC: Call up the Start menu
DOS
Internal commands (4 letters or fewer!!)
- REN: REName, which changes the names of all files within the path (folder) set at the command prompt according to the specified conditions. -> It is only possible within the same directory, but an error may occur if a file with the same name is added -> The command statement in the form ‘REN [filename1] [filename2]’ RENames [filename1] as [filename2], so if the new [filename2] that will replace [filename1] as instructed already exists in the same directory, [filename2] will be duplicated within the directory and an error will occur.
- DIR (view list): /OE: Output in alphabetical order of file extensions /S: Output all files, including those in the specified directory and subdirectories /P: Output by screenful and pause /ON: Ascending order by name /W: Display file names and extensions in 5 columns per line
External commands (5 letters or more!!)
UNIX
- lp : Print text
- cat : Display the contents of a file on the screen.
- chown : Change the owner or group (ownership) of a file. (choose own)
- pwd : Display the path of the current working directory (path way directory)
Components
- Kernel: Manages hardware such as the CPU, memory, and hard disk, providing functions such as scheduling, memory management, file management, and a system call interface / the core component of the OS / main memory / MSDOS.SYS of DOS - Shell: Command interpretation / COMMAND.COM of DOS - Utilities : Commands Order
Characteristics
- Kernel, Shell, File system
Subject 4: General Information and Communications
Information and communications network: An organizational network that processes, stores, or transmits information by utilizing communication facilities, electronic computing organizations, and technologies for using electronic computing organizations
PSC: PCS (Personal Communication Service) is interpreted in Korean as a personal mobile phone.
-In the OSI 7-layer model of an open system, the order of functional layers related to the network structure: Physical layer - Data link layer - Network layer - Transport layer - Session layer - Presentation layer - Application layer