Computer Science Systems Architecture Review

These flashcards cover core concepts of computer architecture, binary arithmetic, signed number representations, floating-point standards, assembly language operations, and historical milestones in programming.

What is the difference between a number, a numeral, and a digit?

A number is an abstract idea (e.g., forty-two), a numeral is the symbol used to write it (e.g., 42 or XLII), and a digit is an individual symbol within a numbering system.

How is the value of a digit determined in positional notation?

The value depends on its position, where each position is worth the base raised to the power of that column number.

Who is credited with describing binary in 1703?

Gottfried Wilhelm Leibniz.

Define bit, nibble, and byte.

A bit is a single binary digit; a nibble is a group of 4 bits; a byte is 8 bits (two nibbles).

What are the unsigned and signed ranges for a standard byte?

The unsigned range is $0$ to $255$, and the signed range is $-128$ to $127$.

What is a 'word' in CPU architecture?

A group of bytes the CPU handles as a single unit, typically sized as 16-bit, 32-bit, or 64-bit depending on architecture.

How many binary bits map to exactly one hexadecimal digit?

Every 4 binary bits map exactly to one hex digit.

What are the four basic rules for binary addition?

$0+0=0$, $0+1=1$, $1+0=1$, and $1+1=0 \text{ carry } 1$.

In a signed binary number, what do the values of the sign bit represent?

The sign bit (leftmost bit) indicates positive if it is $0$ and negative if it is $1$.

Describe the two-step process for negating a number using Two's Complement.

(1) Flip all the bits of the number, then (2) add $1$.

What is the primary advantage of Two's Complement over Sign Magnitude?

Two's Complement has only one representation of zero and allows the same addition circuit to work for both positive and negative numbers without special subtraction hardware.

What is 'sign extension' and how is it performed?

Sign extension is expanding a binary number to a larger type by padding the left side with copies of the sign bit ($0\text{s}$ for positive, $1\text{s}$ for negative).

What is the limitation of Fixed-Point decimal representation?

It is wasteful; for example, if the integer part is always $0$, those bits are kept even if they are unused, and it only allows a small range of fractional values.

How does Floating-Point representation differ from Fixed-Point?

In Floating-Point, the decimal point (radix point) is not fixed but floats based on scientific notation, allowing the system to cover an enormous range efficiently.

What are the three components of a 32-bit IEEE-754 single-precision float?

1 sign bit, 8 exponent bits, and 23 mantissa bits (the 24th bit is implied).

Define Assembly Language.

A low-level programming language where each line corresponds almost directly to one CPU operation, using mnemonics to replace raw binary opcodes.

Why must registers be zeroed out or initialized before use?

Registers hold whatever the previous program left in them (random garbage), and operating on uninitialized registers leads to unpredictable results.

Why is the HLT (halt) instruction placed at the end of a program?

It signals a clean stop to prevent the CPU from executing random bytes in memory as instructions, which could lead to a crash.

Why is the indirect addressing offset in this specific processor limited to $-16$ to $+15$?

Within the instruction byte, $3$ bits specify the register, leaving $5$ bits for the offset, which provides $32$ unique values ($-16$ to $+15$).

What do the representations 0x3, 0x03, and 0x0003 imply to a programmer?

They imply different memory sizes: $0x3$ implies 4 bits, $0x03$ implies 8 bits (1 byte), and $0x0003$ implies 16 bits (2 bytes).

What was the contribution of Grace Hopper to computing?

She built the first compiler.

What is specialized about the programming language FORTRAN created by John Backus?

It is a high-level language that uses structured expressions.

Which historical figure designed Pascal to enforce good programming habits and structured flow?

Niklaus Wirth.

Who co-created UNIX and developed the C programming language?

Dennis Ritchie and Ken Thompson.

What is the result of the logical operation XOR when both values are the same?

The result becomes $0$.