Problem Statement

CSV spreadsheet files are suitable for storing tabular data in a relatively portable way. The CSV format is flexible but somewhat ill-defined.
For present purposes, authors may assume that the data fields contain no commas, backslashes, or quotation marks.

Read a CSV file, change some values and save the changes back to a file. For this task we will use the following CSV file: Suggestions

Let's start with the solution:

OPEN "manip.csv" FOR INPUT AS #1
OPEN "manip2.csv" FOR OUTPUT AS #2

LINE INPUT #1, header$
PRINT #2, header$ + ",SUM"

WHILE NOT EOF(1)
    INPUT #1, c1, c2, c3, c4, c5
    sum = c1 + c2 + c3 + c4 + c5
    WRITE #2, c1, c2, c3, c4, c5, sum
WEND

CLOSE #1, #2
END