Understanding ROM Programming: The One-Time Write Challenge

Read-Only Memory (ROM) is a type of non-volatile computer memory that holds data permanently. Unlike Random Access Memory (RAM), data on ROM cannot be easily altered or erased once written. Different types of ROM exist, each with unique characteristics regarding how and when data is written onto them.

Exploring Different ROM Types

Let's examine the types of ROM mentioned in the options to understand their programming methods:

• Mask ROM: This type of ROM is programmed by the manufacturer during the fabrication process using a physical mask. It cannot be changed or programmed after manufacturing.
• EPROM (Erasable Programmable Read-Only Memory): EPROMs can be programmed by the user, erased using ultraviolet (UV) light, and then reprogrammed. The erasing process requires removing the chip from the device.
• EEPROM (Electrically Erasable Programmable Read-Only Memory): EEPROMs can be erased and reprogrammed electrically, byte by byte or in blocks, without needing to be removed from the device. This allows for multiple rewrites.
• PROM (Programmable Read-Only Memory): A PROM chip comes blank from the manufacturer. It can be programmed by the user exactly *once* using a special device called a PROM programmer. Once a memory location is programmed (often by burning a fuse or changing a transistor state), it cannot be altered or erased.

Identifying the ROM Programmed Only Once

The key characteristic asked in the question is the ability to be programmed only once after manufacturing. Based on the definitions above:

• Mask ROM is programmed *during* manufacturing, not after.
• EPROM and EEPROM can be programmed, erased, and reprogrammed multiple times.
• PROM fits the description perfectly, as it allows a single programming session after manufacturing.

Therefore, the specific type of ROM that can be programmed only once after manufacturing is PROM.