	Includes REM contents	Includes spaces	Control Chars?	Other?	Case-sensitive?	Operation	Grouping(s)	Checksum Size	Program Total
Compute! Automatic Proofreader	Yes	No	CTRL+D	N/A	Yes	Input Buffer	Line	1 byte	No
Nibble Checkit	No	In strings	In Strings	"?"	Yes	Input Buffer	Line, Program	1 byte (line) 2 bytes (program)	Yes, on line numbers
Nibble Apple Checker	Yes	No	CTRL+D	N/A	Yes	Program	Program	1 byte (2 bytes length)	Yes, checksum and length calculation
MicroSPARC Key Perfect 2	Yes	Yes	All	N/A	Yes	Program	Groups of 10 lines, Program	Max 3 bytes	Yes, byte count
MicroSPARC Key Perfect 4	Yes	No	CTRL+D	N/A	Yes	Program	Groups of 10 lines, Program	Max 3 bytes	Yes, byte count
MicroSPARC Key Perfect 5	No	No	CTRL+D	N/A	No	Program	Groups of 10 lines, Program	4 bytes	Yes

Includes REM contents - most checksum algorithms includes the REM as well as the contents of the REM statement; some only include the REM itself.
Includes spaces - indicates if whitespace is important.
Control Chars? - indicates if any control characters are included in the checksum.
Other? - Checkit replaces "?" with "PRINT" to standardize the shortcut for the PRINT statement. The catch is that it ignores quotes. So any "?" is replaced with "PRINT" for the checksum algorithm.
Case-sensitive? - is "A" and "a" handled differently?
Operation - if "Input Buffer" is specified, the checksums are displayed after a line of code has been entered; otherwise, the program must be completed and saved before running checksum.
Groupings - what, if any, groupings apply.

Binary

	Includes spaces	Other?
Compute! Automatic Proofreader
Nibble Checkit	Yes	Yes
Nibble Apple Checker	No	N/A
MicroSPARC Key Perfect 2	No	N/A
MicroSPARC Key Perfect 4
MicroSPARC Key Perfect 5

Includes spaces - indicates if spaces are important. For instance, Nibble Checkit uses the input buffer and does not ignore spaces. Thus, if extra spaces are includes like "0300:A900", the checksum will be off.
Other? - Checkit does the program total against the program bytes, not the entered text. Only the line checksum uses the input buffer.

References