Avg. time to read the data = 0.8(50) + 0.2(300+50) = 40 + 70 = 110 ns
Avg. memory access time = (Seq. of data read request * time to read data) + (freq. Of data write request * time to write the data)
= (0.75 × 110) + (0.25 × 300)
⤿Since write through is mentioned in question. So write operation will take place in memory and not in cache.
= 82.5 + 75.0
= 157.5 ns

Software interrupt is caused either by an exceptional condition in the processor itself, or a special instruction in the instruction set which causes an interrupt when it is executed.
It is used for switching from a CPU user mode to supervisor mode.
Software interrupts is internal interrupt triggered by some software instruction.
There are 8 software interrupts in 8085 microprocessor. They are – RST 0, RST 1, RST 2, RST 3, RST 4, RST 5, RST 6, RST 7.
External interrupt: External interrupts are the interrupts caused by the hardware module. pressing a key on the keyboard or moving the mouse triggers hardware interrupts that cause the processor to read the keystroke or mouse position.

If we have 3 characters then the space between two characters will be 2. It means if we have “n” characters in a line then the number of spaces in the line will be “(n-1)”.
So, the time to print a character line = (200*6)+(199*2)
= 1598 ms
= 1598*10^-3 second
= 1.59 seconds
Printing speed of the dot matrix printer in characters per second
= 200/ 1.59 character per second
= 125.78 character per second

XCNG: Exchange instruction does not change any flag.
SUB: Subtraction instruction will change all the flags.
STC: Set carry instruction will affect the carry flag only.
DCR: Decrement instruction will decrease the value hence it will effect all flags but not carry flag.

LXI B, 0007 H // Load register pair B with value (00)_H and C with value (07)_H
LOP :
DCX B // Decrement register pair BC i.e. decrease C because B is already 0.
MOV A, B // Move value of B to A. It means A is 0 after first iteration of loop LOP.

ORA C // It means perform OR operation between register A and C and store the result into register A. So A = (06)_H after first iteration of loop.
JNZ LOP // Jump to LOP if it is not zero.

So this way LOP will be executed 7 times.

Since MSB of 8-bit result is zero, it means the number is positive. So Sign flag will be “0”.
Since 8-bit result contain zero only so Zero flag will be “1”.
Since addition operation is resulting into a carry so Carry flag will be “1”.

Location Transparency: The name of a file does not reveal any hint of the file's physical storage location i.e. it makes the user, programmers to treat the data as if it is present at one location.

Write-Ahead Log: When in-place updating is used, it is necessary to use a log for recovery. In this case, the recovery mechanism must ensure that the before image of the data item is recorded in the appropriate log entry and that the log entry is flushed to disk before the before image is overwritten with the after image in the database on disk. This process is generally known as write-ahead logging.
Checkpoint is a mechanism where all the previous logs are removed from the system and stored permanently in a storage disk. Checkpoint declares a point before which the DBMS was inconsistent state, and all the transactions were committed.
Log Buffer: A log buffer is a circular buffer that holds information about changes made to the database.

A⁺ = { A, B, C, D}
E⁺ = {E}

Tablet, joystick are continuous devices.
Light pen and touch screen are direct devices.
Keyboard, locator are logical devices.
Data globe and sonic pen are 3D interaction devices.

Cavalier Projection: The direction of projection is chosen so that there is no foreshortening of lines perpendicular to the xy plane.
Cabinet Projection: The direction of projection is chosen so that lines perpendicular to the xy planes are foreshortened by half their lengths.
Isometric Projection: The direction of projection makes equal angles with all of the principal axis.
Orthographic Projection: Projections are characterized by the fact that the direction of projection is perpendicular to the view plane.