Refined CS 244 A1

Translation

Turns a whole program into another language before it runs (like compiling).

Interpretation

Runs the code directly, one line at a time, no translation step.

Microcode

The CPU's own tiny built-in instructions that carry out each of its "real" instructions.

Von Neumann architecture

One memory holds both the program and the data.

Von Neumann bottleneck

The slowdown from having just one bus shared by instructions and data.

Moore's Law

Chip transistor counts roughly double every ~2 years.

Registers

Tiny, super-fast storage spots built right into the CPU.

ALU

The part of the CPU that does the math and logic.

Control Unit

The part of the CPU that directs fetch, decode, and execute.

Fetch (cycle step)

Grab the next instruction from memory.

Decode (cycle step)

Figure out what that instruction means.

Execute (cycle step)

Actually carry it out.

RISC

Simple, small, fixed-size instructions, built for speed and pipelining.

CISC

Complex, variable-size instructions that do more per instruction, harder to pipeline.

Pipelining

Overlap instructions like a factory line, so more finish per second.

Superscalar architecture

Run more than one instruction at once using extra hardware.

Big-endian

Store the biggest byte first.

Little-endian

Store the smallest byte first.

Track

A ring on a disk platter.

Sector

A slice of a track.

Cylinder

The same track, stacked across every platter.

Platter

The actual spinning disk.

Seek time

Time for the head to move to the right track.

Rotational latency

Time waiting for the disk to spin to the right spot.

RAID 0

Splits data across disks for speed, no safety net.

RAID 1

Mirrors the same data on two disks.

RAID 5

Splits data plus a bit of backup info (parity); survives 1 disk dying.

RAID 6

Like RAID 5 with extra backup info; survives 2 disks dying.

ASCII

Basic English letters/numbers, 7 bits each.

Unicode

Every character in every language gets its own number.

UTF-8

Stores Unicode characters using 1-4 bytes each.

auto storage class

Default local variable; lives and dies with the function call.

static storage class (local var)

Local variable that remembers its value between calls.

extern storage class

Says "this variable is actually defined somewhere else."

register storage class

Old hint to keep a variable in the CPU for speed.

Array decay

An array's name basically turns into a pointer to its first item.

Preprocessor's role

Text substitution before real compiling starts (#include, #define).

Prefix (++x)

Increase first, then use the new value.

Postfix (x++)

Use the value first, then increase it.

First-class feature

Something you can store in a variable, pass around, and return, just like any other value.

Covariance

Sub-types keep the same order when built into something bigger.

Invariance

No such order is guaranteed; types must match exactly.

Pointer width

How many bytes a pointer takes, fixed by the system (4 on 32-bit, 8 on 64-bit).

malloc

Ask for a chunk of memory on the heap.

free

Give that memory back.

Memory leak

Forgot to free it, and lost the only way to find it again.