Friday, November 13, 2009 1:13 AM,

In correcting one of the programs turned in for program 2, we noticed that at 
least one student used a label that is off-limits.

I did say this in class, but just in case you missed it: You have a lot of 
freedom to come up with labels that make sense.  One set of words that can not 
be used are words that have a different meaning to the assembler, such as the 
opcodes (ADD, TRAP, JSR, etc.) or HALT, GETC, IN, RET, etc.  
We call such words "reserved words."  They would confuse the assembler and 
that is not allowed.  

Recall that the assembler is looking at ASCII codes corresponding to 
characters, character by character.  If we allowed HALT to be a label, how 
would the assembler know whether we wanted it to create a symbol table entry 
or generate the bit pattern 1111 0000 0010 0101 ?

Since the assembly code MUST be unambiguous, we adopt the rule that reserved 
words in the assembly language can not be used as labels. 

Something to keep in mind as you create meaningful labels.

Good luck on the 2nd exam.

Yale Patt