added info

added requirements section, examples for running the program, and
updated formatting

README.md

@@ -1,17 +1,29 @@
 ## About ##
-batch_retrieval.py downloads images from Chronicling America. It works in three steps:
+batch_retrieval.py downloads newspaper page images from Chronicling America. It works in three steps:
 
-1. Create the master manifest of every newspaper image in the Chronicling America collection
-2. Download the images. The getImages function can take in two integers that correspond to the beginning year and ending year that you want to download from (dates of newspapers).
-3. Convert images from JP2000 to .jpg
+1. Creates the master manifest of every newspaper page image in the Chronicling America collection
+2. Downloads requested images. The getImages function takes in two integers that correspond to the beginning year and ending year that you want to download images for (publication dates of newspapers).
+3. Converts downloaded images from JP2000 to .jpg
 
-All images are stored in a file hierarchy based on the Chronicling America file hierarchy.
+All downloaded images are stored in a file hierarchy based on the Chronicling America file hierarchy.
+
+## Requirements ##
+* Java version 7 or higher  
+* Python version 2.7 (not Python 3)  
+* Python image dependencies:  
+  * JasPer (JP200 Python encoder/decoder)  
+  * Pgmagick (Python image library)
 
 ## Running ##
-Run the retrieval by running:  
-`python Batch_Retrieval.py <flag> <begin year> <end year>`
-
-use <flag> to specify which functions to run:  
-* flag = 1 for run build manifest, get images and convert to *.jpg
-* flag = 2 for get images and convert to *.jpg (use if manifest already exists)
-* flag = 3 for build manifest only 
+To run the retrieval program:  
+`python batch_retrieval.py <flag> <begin year> <end year>`
+
+Use one of the following `<flag>` values to specify which function(s) to run:
+* flag = 1: Run all steps. Build manifest, get images from a specific year or years, and convert to .jpg.  
+**Example:** `python batch_retrieval.py 1 1924 1924` [Creates complete manifest, downloads all images from 1924, and converts those images to .jpg]  
+**Example:** `python batch_retrieval.py 1 1836 1840` [Creates complete manifest, downloads all images from 1836-1840, inclusive, and converts those images to .jpg]  
+* flag = 2: Get images from a specific year or years and convert images to .jpg (can only be run independently if manifest already exists).    
+**Example:** `python batch_retrieval.py 2 1924 1924` [Manifest already exists; downloads all images from 1924 and converts those images to .jpg]  
+**Example:** `python batch_retrieval.py 2 1836 1840` [Manifest already exists; downloads all images from 1836-1840, inclusive, and converts those images to .jpg]
+* flag = 3: Build manifest (do not download and convert images). Do not specify a begin year or end year, as the manifest builder always compiles the complete manifest for all images in the Chronicling America collection.  
+**Example:** `python batch_retrieval.py 1` [Creates a complete manifest all of newspaper page images in Chronicling America and saves manifest for later use.]