TAP Format

Tags:

spectrum File Format

The .TAP file format is a container used to store data in a format identical to the Spectrum's SAVE rom routine.

.TAP files can be concatenated together so forming a new tape is as easy as joining multiple .TAP files together to form a new one. For example on Linux or MacOS:

1cat part1.tap part2.tap > final.tap

In DOS and Windows:

1copy /b part1.tap + part2.tap final.tap

At a bare minimum, a .TAP file consists of two blocks; a header block followed by a data block.

Each block consists of the Block Wrapper which then contains data within it.

Block Wrapper

Header and Data blocks consists of a 2-byte word with the length of the block (including the checksum), the block type, then the block's data and finishing with a single checksum byte.

The block type is either 0x00 for a Header and 0xFF for a Data block.

The checksum byte is in reality a binary XOR of all bytes in the block and not a true checksum.

Byte	Field Description
	70Length of block
	158n
0	Block Type
1	n-2 bytes of data

n-1	Check sum byte

Header Block

The header block defines the type, filename, length and additional information about the file.

The file name is up to 10 characters padded with spaces.

The length at offset 11 is the number of bytes data in the data block. This excludes the block type and checksum byte.

Parameter's 1 and 2 are determined by the file type. If not used then they are set to 0.

Byte	Description
0	File Type
1	File Name padded with spaces
2

9
10
11	70Length of data block
12	158
13	70Parameter 1
14	15	Name for types 1 and 2	8
15	70Parameter 2
16	158

Type	File Description	Param 1	Param 2
0	BASIC Program	Line number to start	Start of variable area relative to program start
1	Number Array	Variable name, e.g. if `DIM a()` then this is 0x80 a=0x81, y=0x99
2	Character Array	Variable name, e.g. if `DIM a$()` then this is 0x80 a=0xC1, y=0xD9
3	CODE	Start when saved	32768

Data Block

For BASIC programs (type 0) the data block consists of a series of lines stored as it is in memory, i.e. in it's tokenised state.

For CODE files it consists of the raw bytes in the order they appear in memory.

For both array types they have a specific structure which won't be described here as they are not of any real use outside a basic program. Only types 0 and 3 are of any use these days.

Examples

An example of creating a .TAP file is available, which shows a basic loader which then loads a Machine code program.

Last modified November 3, 2021: Add TAP file format, and a Hello World example for zasm utilising a simple basic loader, which can be reused as the precompiled .tap files are also included (cf3e09a)