RAM, ROM and memory types
| English | Chinese | Pinyin |
|---|---|---|
| RAM | 随机存取存储器 | suí jī cún qǔ cún chǔ qì |
| ROM | 只读存储器 | zhī dú cún chǔ qì |
| volatile | 易失性 | yì shī xìng |
| non-volatile | 非易失性 | fēi yì shī xìng |
| firmware | 固件 | gù jiàn |
| SRAM | 静态RAM | jìng tài RAM |
| DRAM | 动态RAM | dòng tài RAM |
| cache | 高速缓存 | gāo sù huǎn cún |
| capacitor | 电容器 | diàn róng qì |
| EEPROM | 电可擦可编程只读存储器 | diàn kě cā kě biān chéng zhī dú cún chǔ qì |
The two main memories
- A computer's main memory comes in two flavours: RAM 随机存取存储器 and ROM 只读存储器.
- Within RAM there are two technologies; ROM has several programmable variants.
- The key idea is volatile 易失性 (loses data without power) vs non-volatile 非易失性.
Device and storage lab
Classify computing examples by what job they do in a system.
RAM vs ROM
- RAM (random access memory) — volatile: loses its contents without power. Holds the OS, running programs and their data; read and written constantly.
- ROM (read-only memory) — non-volatile: keeps data without power. Usually written once; holds the firmware 固件 needed at start-up (the BIOS / boot loader).
- So ROM starts the system; RAM then holds the active work.
A RAM module (DIMM) is the computer's fast main memory, plugged into the motherboard.
Which statement is true?
RAM loses its contents without power (volatile); ROM keeps them (non-volatile).
ROM typically holds:
ROM is non-volatile and written once, so it stores the start-up firmware. Running programs live in RAM.
Put the start-up sequence in order.
ROM is non-volatile so its firmware is there at power-on; it then loads the OS into volatile RAM.
SRAM 静态RAM vs DRAM 动态RAM
- SRAM stores each bit in a flip-flop of several transistors. Fast, but expensive and not dense → used for CPU cache 高速缓存.
- DRAM stores each bit as charge on a tiny capacitor 电容器. Cheaper and denser but slower, and must be refreshed thousands of times a second → used for main memory.
RAM is volatile and read/write; ROM is non-volatile and read-only
SRAM is fast but expensive, so it is mainly used for:
SRAM (flip-flops) is fast but not dense, ideal for small fast cache. DRAM is used for large main memory.
DRAM must be refreshed (rewritten) thousands of times a second to keep its data.
DRAM stores each bit as charge on a capacitor, which leaks away — so it is constantly refreshed. SRAM does not need this.
Match each memory type to its key trait.
RAM/ROM split on volatility; SRAM/DRAM split on speed vs density.
PROM, EPROM and EEPROM 电可擦可编程只读存储器
- PROM — written once (fuses burned by a programmer); cannot be changed.
- EPROM — erased by strong UV light, then rewritten (the whole chip at once).
- EEPROM — erased and rewritten electrically, a byte at a time, in circuit. Flash memory is a derivative optimised for fast block erase.
EEPROM differs from EPROM because it can be:
EEPROM is erased electrically a byte at a time in place; EPROM needs UV to erase the whole chip; PROM is write-once.
You've got it
- RAM = volatile (running programs); ROM = non-volatile (start-up firmware)
- SRAM (flip-flops, fast) → cache; DRAM (capacitor, needs refresh) → main memory
- PROM write-once; EPROM UV-erased; EEPROM electrically erased a byte at a time (flash = block erase)