How to read a CSV file in ALGOL?

Reading a CSV file in ALGOL, a high-level computer programming language, requires a careful approach as the language does not natively support file structure like CSV. Here's a simple guide on how you can achieve this:

Step 1: The first thing you would need is ALGOL 68's mode, a data type such as INT (integer), REAL (floating-point number), etc. To create a CSV reading module, you will have to define new modes to handle string data input (STRING) and the FLEX (flexible array) mode for string buffers that can change in size.

Step 2: CSV data format has a nature of tabular data, where each line presents a row and data is often separated by commas. Knowing this, we need to parse the data file by lines and comma-separated sections. Consider the methods new line() and next comma(). new line() jumps to the start of the next line until no lines are left, while next comma() skips to the next comma in the current line.

Step 3: Define procedures as needed. For instance, the next field procedure can read the characters from the current position to the next comma and convert it into a string. Make sure to handle edge cases like end of the line or end of the file.

Step 4: With your fields ready as STRING you can convert them to different types as needed. For instance, ALGOL character variables can be converted into numeric variables using inbuilt functions, such as whole or real.

Step 5: Now you can create a main reading loop for handling all the lines in your CSV file sequentially. Using a combination of the functions you’ve created before, you can now effectively read CSV files into your ALGOL program.

Please note that ALGOL is largely obsolete language and has gone through several revisions. Given its declining usage and support, it is recommended to consider modern languages like Python for text and file handling tasks.

This solution assumes we are discussing ALGOL 68, the latest revision of the language. If you are working with a different revision of ALGOL, the approach may vary and could be significantly complicated, as earlier revisions (e.g., ALGOL 60) had less support for string manipulation and I/O handling. It's important that you confirm the specific version of ALGOL you are using and pay close attention to the specific syntax and functionality details of that version.