In this screenshot, I have little code on left that make immediate addressing on the R register. When I load the code that throw this error, But on CPU Emulator have some fine assigning the value #1 to R is looking fine, can't put a value more than one digit.
The format of a C-type instruction is very explicit
The comp MUST BE one of the 28 mnemonics defined in Figure 4-3. There is no mnemonic "100", nor is there a mnemonic "2".
Somewhat unfortunately, the authors' CPU emulator will accept "M+D" as a mnemonic equivalent to "D+M". This is not in strict conformance with the ISA specification, it is because whoever wrote the emulator chose to extend its instruction set to include additional mnemonics that have obvious semantics that are the same as specified mnemonics. This is not optimal because it means that code that will run after being assembled on one person's assembler may not run if assembled on another person's assembler.