Which of the following filename extension suggests that the file is a backup copy of another file?
Answer: D
Correct answer: BAK
The extension .BAK marks a backup copy, written automatically by many programs before they overwrite the original, so the previous version can be recovered. TXT holds text, COM an executable, and BAS a BASIC source file.
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A compiler for a high-level language that runs on one machine and produces code for a different machine is called is
Answer: C
Correct answer: cross compiler
A cross compiler runs on one machine but generates code for another, which is how software is built for a target too small to host a compiler - an embedded processor or a new machine that does not yet run anything. Optimising, one-pass and multipass describe how a compiler works, not what it targets.
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In analyzing the compilation of PL/I program, the term "Machine independent optimization" is associated with
Answer: C
Correct answer: creation of more optimal matrix.
Improving the intermediate representation - removing common subexpressions, hoisting loop-invariant code, folding constants - is done before any target machine is considered, so it belongs to machine-independent optimisation. Register allocation and instruction selection depend on the machine and come later.
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The term 'polling' in a computer means a process by which a computer system
Answer: D
Correct answer: inquires to see if a terminal has any transaction to send
Polling is the controller asking each device or terminal in turn whether it has anything to send, and moving on if it has not. It costs processor time whether or not there is work, which is why interrupts are preferred where the hardware supports them.
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Batch files contain a group of MS-DOS commands that are run in successive order. What filename extension identifies batch files?
Answer: B
Correct answer: BAT
A batch file carries the extension .BAT, and DOS recognises it as a list of commands to be executed one after another rather than as machine code. COM and EXE hold executable programs, and SYS holds device drivers and system files.
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A task in a blocked state
Answer: D
Correct answer: is waiting for some temporarily unavailable resources
A blocked process is waiting for something that is not yet available - the completion of an input operation, or a semaphore held elsewhere. It is not executable and does not belong in the run queue: the scheduler will not consider it again until the event it waits for occurs and moves it back to ready.
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Which command of DOS is used to compare two floppy disks?
Answer: B
Correct answer: DISKCOMP
DISKCOMP compares two diskettes track by track and sector by sector, reporting where they differ - the usual check after a DISKCOPY. DISKCOPY duplicates a disk rather than comparing.
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Under virtual storage,
Answer: C
Correct answer: only the active pages of a program are stored in primary storage
Virtual storage keeps only the pages a program is currently using in main memory and leaves the rest on disk, fetching each as it is referenced. A program can therefore be larger than the memory available, and the memory can be shared among more programs than would otherwise fit.
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The advantage(s) of incorporating the macro processor into pass 1 is(are):
Answer: D
Correct answer: all of the above
Building the macro processor into pass 1 of the assembler avoids implementing input, output and table handling twice, avoids writing an intermediate file between the two programs, and gives the programmer more flexibility, since macro definitions and assembler statements may be interleaved freely. All three advantages follow from the merge.
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For how many processes which are sharing common data, the Dekker's algorithm implements mutual exclusion?
Answer: B
Correct answer: 2
Dekker’s algorithm was the first correct software solution to mutual exclusion, and it works for exactly two processes. It combines two intention flags with a turn variable, so that when both want to enter the turn variable breaks the tie and neither can be starved. Generalising it to \( n \) processes needed Dijkstra’s and later Lamport’s work.
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