define an array with 12 month/rows and 31 days/columns for a year's temperature data in a main function.

One subtask is to write a function and call it from main reading a text file with mean temperature data of one year and store read data into this array.

For example, when you read the temperature 15.4 degrees at date 23.11.2017 you can store double value 15.4 in array row 11 and column 23 as index.
how i can make the program know thiss the temperature value even in the file seems like this 23.11.2017,15.4

Try out yet again. Demonstrate your function and avoid pasting research Directions as that Appears demanding.