C-DAC C-CAT flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Subject-verb agreement with phrases

A verb agrees with the true subject, not with a noun inside a modifying phrase. In "The box of pens is heavy", the subject is "box", so the singular verb "is" is correct.

Present perfect vs past simple

Present perfect (has/have + past participle) describes a past action with present relevance and cannot take a finished-time marker like "yesterday". Past simple is used for completed actions at a definite past time.

Third conditional form

If + past perfect, then would have + past participle. It describes an unreal past situation and its unreal past result, as in "If she had studied, she would have passed".

Affect vs effect

"Affect" is normally a verb meaning to influence. "Effect" is normally a noun meaning a result. "The drug affected his mood" and "the effect was mild" show the standard uses.

Comprehension distractor pattern

Wrong options often copy exact words from the passage while changing the relation between them, such as reversing cause and effect or turning a possibility into a certainty. The correct option paraphrases.

Letter position arithmetic

Letters map to 1-26 (A=1, Z=26). Opposite letters sum to 27, so A pairs with Z and C with X. Reverse value equals 27 minus forward value.

Syllogism validity rule

A conclusion is valid only if it is true in every possible diagram of the premises. "All A are B" does not prove "all B are A" or that any A exists.

Blood relation decoding

Convert each phrase into a tree link: father's brother is uncle, sister's son is nephew, mother's brother's daughter is cousin. Track gender and generation separately before answering.

Direction sense displacement

Fix north upward and rotate turns accordingly. For a non-straight path, net displacement is the straight-line distance found with Pythagoras from total north-south and east-west movement.

Alternating series rule

When first differences show no pattern, split the series into odd-position and even-position terms. Each sub-series may follow its own rule, such as adding 3 and multiplying by 2 alternately.

Euler path figure test

A figure can be drawn in one stroke without retracing only if it has zero or two vertices of odd degree. More than two odd vertices makes a single-stroke drawing impossible.

Successive percentage change

Two successive changes a% and b% produce a net change of a + b + ab/100 percent. A 20% increase then a 20% decrease gives a net 4% decrease, not zero.

Profit percentage base

Profit percent equals (SP minus CP) divided by CP, times 100. It is computed on cost price unless the question explicitly states selling price as the base.

CI minus SI for two years

For two years at rate R, compound interest exceeds simple interest by P times (R/100) squared. At 10% on 1000, the gap is 10.

km/h to m/s conversion

Multiply kilometres per hour by 5/18 to get metres per second, and multiply metres per second by 18/5 to return. So 72 km/h equals 20 m/s.

Train crossing a platform

Total distance covered is train length plus platform length. Time equals that sum divided by speed, with speed converted to metres per second first.

Boats and streams formulas

Downstream speed is boat plus stream, upstream is boat minus stream. Boat speed is half the sum of downstream and upstream; stream speed is half their difference.

Alligation ratio rule

To mix components priced cheaper and dearer to reach a mean price, the quantity ratio is (mean minus cheaper) to (dearer minus mean). The cheaper component gets the larger share.

Combined work formula

If A alone finishes in a days and B alone in b days, working together they finish in ab divided by (a + b) days, assuming their rates simply add.

Cone slant height

For a right circular cone, slant height l equals the square root of r squared plus h squared. Curved surface area is pi times r times l, and volume is one third pi r squared h.

Two's complement negation

Invert every bit of the binary number and add 1 to obtain its negative. An 8-bit signed integer therefore ranges from minus 128 to positive 127.

Binary to hexadecimal grouping

Group binary digits in fours from the right, then replace each group with one hex digit. Thus 1011 1110 becomes BE, since 1011 is B and 1110 is E.

Universal logic gates

NAND and NOR are called universal because either one alone can build AND, OR and NOT. XOR gives 1 only when its two inputs differ.

Memory hierarchy order

From fastest and smallest to slowest and largest: CPU registers, cache levels, main RAM, then secondary storage such as SSD and hard disk. RAM loses contents on power loss.

Binary size prefixes

One byte is 8 bits. One kilobyte is 1024 bytes, one megabyte is 1024 kilobytes, and one gigabyte is 1024 megabytes. Two hex digits encode exactly one byte.

Pre-increment vs post-increment

In C, ++x increments x before its value is used in the expression, while x++ uses the current value first and increments afterward. The final value of x is the same.

Short-circuit evaluation

In C, the && and || operators stop evaluating once the result is known. If the left operand of && is false, the right operand is never executed.

C string null terminator

A C string is a character array ending with the null character backslash-zero. The word "cat" occupies four bytes: three letters plus the terminator.

for loop execution order

A C for loop runs initialization once, then repeats: test the condition, execute the body if true, run the update. The loop exits when the condition becomes false.

Fetch-decode-execute cycle

The CPU repeatedly fetches an instruction from memory at the program counter, decodes its operation, executes it, and stores any result, then advances to the next instruction.

IPv4 vs IPv6 length

An IPv4 address is 32 bits long, usually written as four dotted decimal octets. An IPv6 address is 128 bits long, written as eight groups of hexadecimal digits.

Zero-indexed array access

In C, an array of n elements has valid indices 0 through n minus 1. Accessing index n or beyond reads memory outside the array and is undefined behaviour.