underscore in my alphabet for finite state automata table

Question

I am tasked with a program that is a scanner. My alphabet is as follows:

all english letters (upper and lower), digits, 
plus the extra character _ (underscore) & ws. Identifier begins with a letter and can 
continue with any number of letters, digits or _ up to 10 significant characters.

I am wanting to make sure my table is correct. For some reason my scanner is not working with the underscore. I can get it work for letters and digits. I am trying to narrow down my problem and wanting to make sure it is not the table.

Here is my table, just a partial part:

// state token      ws    L   D   _   
 {   0,  0,         0,    1, 11,  21, 
 {   1,  id_tk,    -1,    2,  2,   2,
 {   2,  id_tk,    -1,    3,  3,   3,
 {   3,  id_tk,    -1,    4,  4,   4,
 {   4,  id_tk,    -1,    5,  5,   5,
 {   5,  id_tk,    -1,    6,  6,   6,
 {   6,  id_tk,    -1,    7,  7,   7,
 {   7,  id_tk,    -1,    8,  8,   8,
 {   8,  id_tk,    -1,    9,  9,   9,
 {   9,  id_tk,    -1,   10, 10,  10,
 { 10, id_tk,      -1,   -2, -2,  -2,
 { 11, num_tk,     -1,   -1, 12,  -2,
 { 12, num_tk,     -1,   -1, 13,  -2,
 { 13, num_tk,     -1,   -1, 14,  -2,
 { 14, num_tk,     -1,   -1, 14,  -2,
 { 15, num_tk,     -1,   -1, 15,  -2,
 { 16, num_tk,     -1,   -1, 16,  -2,
 { 17, num_tk,     -1,   -1, 17,  -2,
 { 18, num_tk,     -1,   -1, 18,  -2,
 { 19, num_tk,     -1,   -1, 19,  -2,
 { 20, num_tk,     -1,   -1, 20,  -2,
 { 21, undrs_tk,   -1,   -2, -2,  -2,

Legend is as follows:

WS = whitespace
L = letter
D = digit
_ = underscore

-1 = final state
-2 = error state

Is this table correct with the above mentioned alphabet? I really appreciate the help. Thanks

Answer 1

Your spec says an identifier has 10 significant characters, which usually means that the identifier can be longer, one just ignores any characters beyond 10 for comparison purposes. Your automaton rejects any identifier that's longer than 10 characters.

Your spec does not specify what num_tk and undrs_tk should be, so I cannot comment on them.

There is no obvious problem with your handling of underscore in the table. If it doesn't work, the problem is likely in your driver code, which you do not show.