Heidi uses her computer to write articles for a newspaper. She uses a program to

Speech synthesis or text-to-speech (TTS) program

Explanation:

A speech synthesis program is a program can convert a written text to audio. The program can recognize the text and present it in audio format with a human voice. Speech synthesis program can be found in Microsoft Word. We can go Review tab and find the "Read Aloud" option. We can selectively highlight the text in Word and click "Read Aloud". This will trigger the text-to-speech conversion process and produce the audio output of the highlighted text in human voice.