ZX-jen screen shot

Here is a screenshot from the "ZX-jen" project, or the Drake-TV mentioned earlier in this blog. The cursor is '>' and the screen continues at the top after it ends at the bottom, instead of scrolling. The square block is the cursor and indicates the current position. Before that is the executing of the program, which is:

10 print "Hello world!"
20 let a%=3

As you can see the result of the execution is:

pHello world!
l%

The "Hello world!" is the actual output, the "p" and "l" are debug indicators: they are the first letter of the command being executed, so "print" and "let". The % sign is the type of variable being read, in this case an integer, which indicates that the let statement was correctly interpreted. The only other command that is currently available is "goto". The "Esc" key can be used to interrupt a program. The next step will be to allow printing of a%, although for that to happen the assignment should actually store the value in memory. After this various simple operations, like + and - should be implemented. After this I will consider the "for" and "next" statements.

As you can see the system supports "run" and "list" commands, but also "new" to wipe the memory. The program is stored in an external 24LC512, so even if the power fails the program will be available. Program lines can be entered by just preceding something with a line number, and deleted by providing a line number with no data. Overwriting is possible too.