If you try to declare an array longer than 512 characters, MASM issues an error:

 error A2039:line too long

How to declare big array for MASM? One large array is needed, not several small ones.

Breaking into several lines, inserting the character ‘ ‘ does not solve the problem.

In this case, it is an array of structures:

.data
       
   sysmet   struc
        iIndex  DB      0
         szLabel    DB      22 DUP (0)
         zero1      DB      0
         szDesc     DB      40 DUP (0)
         zero2      DB      0
    sysmet  ends
        
  sysm  sysmet  <SM_CXSCREEN, "SM_CXSCREEN", 0, "Screen width in pixels", 0>, 
        <SM_CYSCREEN, "SM_CYSCREEN", 0, "Screen height in pixels", 0>,
        <SM_CXVSCROLL, "SM_CXVSCROLL", 0, "Vertical scroll width", 0>,
        <SM_CYHSCROLL, "SM_CYHSCROLL", 0, "Horizontal scroll height", 0>,
        <SM_CYCAPTION, "SM_CYCAPTION", 0, "Caption bar height", 0>,
        <SM_CXBORDER,  "SM_CXBORDER", 0,  "Window border width", 0>,
        <SM_CYBORDER,  "SM_CYBORDER", 0,  "Window border height", 0>,
        <SM_CXFIXEDFRAME, "SM_CXFIXEDFRAME", 0, "Dialog window frame width", 0>

The number of characters in the array declaration reaches 552.
If you remove the last line, the error does not appear.

If added a ‘sysmet’, then the

lengthof sysm

operator returns the number of elements to the first sysmet. This does not suit me. I need to declare an array of large size for which both the number of elements and the size of the structure as a whole will be counted correctly.

The only solution I found at the moment is the initialization of an empty array through the DUP. Then fill in the elements of the array when processing the WM_CREATE message.

sysm    sysmet  74 DUP (<0, ' ', 0, ' ', 0>)

sysmetrics  LABEL   BYTE
            DB SM_CXSCREEN, "SM_CXSCREEN", 0, "Screen width in pixels", 0 
            DB SM_CYSCREEN, "SM_CYSCREEN", 0, "Screen height in pixels", 0
            DB SM_CXVSCROLL, "SM_CXVSCROLL", 0, "Vertical scroll width", 0
        

...

But this is a bad decision. I don’t like it.

The LENGTHOF operator counts the number of elements in a single data declaration. Not to be confused with SIZEOF Operator.

Re: “To calculate the number of elements, divide the size in bytes of all the elements (the difference between the two labels) by the size in bytes of one element.”

Thank you. This is a better solution.

.data
sysmet  struc
     iIndex     DB      0
     szLabel    DB      22 DUP (0)
     zero1      DB      0
     szDesc     DB      40 DUP (0)
     zero2      DB      0
sysmet  ends

sysm    sysmet  <SM_CXSCREEN, "SM_CXSCREEN", 0, "Screen width in pixels", 0>,
            <SM_CYSCREEN, "SM_CYSCREEN", 0, "Screen height in pixels", 0>,
    …
    sysmet  <SM_CMONITORS, "SM_CMONITORS", 0, "Number of monitors", 0>,
            <SM_SAMEDISPLAYFORMAT, "SM_SAMEDISPLAYFORMAT", 0, "Same color format flag", 0>
lenOfSysm   =   $-sysm

.code
    ;cLineNumbers = lenOfSysm / sizeof sysmet
    xor     EDX, EDX
    mov     EAX, lenOfSysm
    mov     EBX, sizeof sysmet
    div     EBX
    mov     cLineNumbers, EAX

But this is still a bypass of MASM restrictions. Microsoft seems to have stopped properly supporting MASM.