Mark IV is a fourth-generation programming language that was created by Informatics, Inc. in the 1960s. It automated the reading of input files and conversion of the data inside to produce one or more reports and updated output files. At the time, this program was called a file management system, though it was not what today is understood by that term (a file manager); rather, it was what today would be known as a report generator.

It was used for roles similar to the COBOL programming language or PL/1, but was far easier to use and the instructions normally consisted of a single piece of paper that was converted to a few punch cards. Customers lauded the product for its time savings, often able to generate one-off reports in a matter of days when weeks or months would be needed with traditional tools.

It is historically important as one of the first examples of commercial software that was sold by an independent vendor. It was also the first software product to break $10 million in cumulative sales, and the first to break $100 million.

John Postley had previously worked as the head of Rand Corporation's Data Processing department, but left in 1960 to work for Advanced Information Systems (AIS), a recently formed programming firm. At Rand he had seen that much of the programming effort being expended was producing reports, and began to wonder if there was a generalized solution to this problem.

He soon found a customer willing to pay them to find out; Douglas Aircraft. Their Missiles and Space Systems division had about 100 different file formats being generated across a suite of IBM machines including IBM 701, 704 and 709's. There was no centralized organization for these systems and each user developed their own programs and formats. In order to streamline their operations, they were replacing many of these systems with an IBM 7090. They hired AIS to move their reports to the new system, and agreed to allow Postley to solve the problem with a "file management system".

The resulting system was known as GIRLS, for Generalized Information Retrieval and Listing System. It was first revealed publicly in December 1962. At the time, it was described as a system that intended to solve the problem of the growing number of programs being run, and especially the number of different files they generated, which could number in the "tens or perhaps hundreds of such files in a single company". Generating reports was normally accomplished in COBOL or one of the many similar programming languages, but as the authors noted, while this was suitable for developing reports that would be run all the time it was far too time consuming for the large number of one-time ad-hoc reports that managers demanded.

A number of report generator programs had been introduced by the early 1960s, but they generally had little or no flexibility to adapt to different file formats. While they were useful for taking the known output of one program and formatting it, they could only be used with one program's file at a time. GIRLS was an attempt to deal with this problem by adding a system to allow the programmer to describe the file format in much more detail, including details on various data types (fields) and the way they could be collected together into large entries (records). These could be described as relative offsets which gave it the ability to handle variant records. The fields themselves could be fixed or variable length, delimited or not, and many other options.

The GIRLS system broke the task into two parts. First, the input and output file formats would be described on a series of punch cards known as the dictionary which would then be compiled into a subroutine that could read that file. In essence, dictionaries were used to convert variant data into a single internal table-like format and given column names. These programs would be saved onto magnetic tape for rapid retrieval. The second part was the "request form", starting on a paper form and then translated to another series of punch cards that described which records should be read from which files, adding optional filters to remove unneeded data, and the calculations that would be carried out on that data. A report is run by loading a request form into the card reader, and the tapes containing the data files onto the drives. The report is then run, which compiles a small program that uses the dictionaries on another tape to read the data from the tapes, perform the requested operations, and generate the output.