Zilog Z80 QWERTY keyboard floppy drives RS-232 parallel port Apple I Microsoft Z80 operating system RAM BASIC Apple II batch processing
The Model I used a Zilog Z80 processor clocked at 1.77 MHz (later specimens shipped with the Z80A). The basic model originally shipped with 4 KB of RAM and Level 1 BASIC produced in-house. RAM in the first 4 KB machines was upgradeable to 16 KB and Level 2 Microsoft BASIC, which became the standard basic configuration. An Expansion Interface provided sockets for further RAM expansion to 48 KB. Its other strong features were its full stroke QWERTY keyboard with numeric keypad (lacking in the very first units but upgradeable), small size, well written Microsoft floating-point BASIC and inclusion of a 64-column monitor and tape deck—all for approximately half the cost of the Apple II. Eventually, 5.25-inch floppy drives and megabyte-capacity hard disks were made available by Tandy and third parties. The Expansion Interface provided for up to four floppy drives and hard drives to be daisy-chained, a slot for an RS-232 serial port and a parallel port for printers. With the (later) LDOS operating system, double-sided 80-track floppy drives were supported, and features such as Disk Basic with support for overlays and suspended/background programs, device independent data redirection, Job Control Language (batch processing), flexible backup and file maintenance, typeahead and keyboard macros.
