here's the code i have so far:

.model small
.stack 100h

.data
    numberPrompt db "Enter a number between 0 and 999: ", 0
    sumRow1Msg db "The sum of row 1 is: ", 0
    sumCol2Msg db "The sum of column 2 is: ", 0
    numGtr100Msg db "The number of values > 100 is: ", 0
    matrix db 4 dup (?)
           db 4 dup (?)
           db 4 dup (?)
           db 4 dup (?)
    count = 16

.code
extrn Writestring:proc, Readint:proc, Writeint:proc, Crlf:proc

main proc
    mov ax, @data
    mov ds, ax

    call GetNums
    call DisplayMatrix
    call sumRow1
    call sumCol2
    call Greater100
    call Swap1W2
main endp

GetNums proc
    mov si, offset matrix
    mov cx, count
    GetData:
        mov dx, offset numberPrompt
        call Writestring
        call Readint
        call Crlf
        mov [si], ax
        add si, 2
        loop GetData
GetNums endp

DisplayMatrix proc
    mov si, offset matrix
    mov cx, 4
    loop:
        mov ax, [si]
        mov bx, 10
        call Writeint
DisplayMatrix endp    

;get sum row 1
sumRow1 proc
    mov si, offset matrix
    mov bx, [si]
    mov cx, 3
    Sum1:
        add si, 2
        add bx, [si]
        loop Sum1
    
    mov  dx,offset sumRow1Msg
    call Writestring
    mov  ax,bx             ; get the sum(in BX)
    mov  bx,10
    call Writeint      ; display it

sumRow1 endp

;get sum col 2
sumCol2 proc
    mov si, offset matrix+1
    mov bx, [si]
    mov cx, 3
    Sum2:
        add si, 4
        add bx, [si]
        loop Sum2

    mov  dx, offset sumCol2Msg
    call Writestring
    mov  ax,bx             ; get the sum(in BX)
    mov  bx,10
    call Writeint      ; display it
sumCol2 endp

; count display number vals > 100
;while (cx < count)
;{
;    if ([si] < 100)
;         count = count + 1
;    cx++
;    si = si +2
;}
Greater100 proc
    mov cx, 1
    While:
        cmp cx, count
        jg Enddo
        cmp [si], 100
        jl L2
        inc bx
    L2:
         inc cx
         add si, 2
         jmp While
    Enddo:
        mov  dx, offset numGtr100Msg
        call Writestring
        mov  ax,bx             ; get the sum(in BX)
        mov  bx,10
        call Writeint      ; display it
Greater100 endp

;swap rows 1 and 2
Swap1W2 proc
    mov si, offset matrix
    mov di, offset matrix+4
    mov cx, 3
    rowSwap:
        mov bx, [si]
        xchg bx, [di]
        mov [si], bx
        add si, 2
        add di, 2
        loop rowSwap
Swap1W2 endp

end main

Hmm,

        call Writestring
        call Readint
        call Crlf
        mov [si], ax


How sure are you that the Crlf routine will NOT trash the contents of ax?

    call sumCol2
    call Greater100
    call Swap1W2

After this.... you're not going to do a DisplayMatrix?  Swap1W2 isn't going to display the matrix...

"Information has a tendency to be free.  Which means someone will always tell you something you don't want to know."