The Lisa protects tools from illegal duplication by the use of the unique serial nunber built into every Lisa. When a tool is first installed, the diskette from which the duplicate came is modified. To illustrate this modification and the method of removing the modification the Macintosh application FEdit will be used. FEdit displays and modifies raw disk blocks on a Macintosh or Lisa Sony 400K diskette. A disk block contains 512 bytes. Numbers in hexadecimal (base 16) are proceeded by a dollar sign ($).

NOTE

This modification can not be done on the Lisa since no Lisa tools exist which allow a person to modify diskettes at the block level.

Every Lisa diskette stores files in a data structure known as the diskette catalog. This catalog begins on block $23 and ends on block $26. The catalog contains entries for each file present on the disk. For Lisa tools, the tool file name has the unique structure

where the xxx refers to a unique number which is assigned to each tool. For example, the LisaCalc tool is stored under the file name "{T3}OBJ". After the diskette catalog appears a single block for every file in the catalog. These blocks contain the information which, when modif ied, deserializes the tool so that it may be used on other Lisas. To find the block which has this tool information use FEdit starting at block $27 and sequentially search for a block which has the tool name you wish to deserialize in the first data line. On my LisaCalc diskette I found this information block at block $2D. The original information appeared as follows: