I was just studying about firewalls and IDS/IPS and had a doubt. Are these the only two major security devices that a company invests in? or are there other equipment and security controls?
Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
There are few other choices. If software is inherently insecure, all you can do is to replace it with something that isn't; or wrap it up in a condom of some sort. Host-based systems require programs to be invasively, and cooperatively, installed on every client (virus scanners, local network stack IPS). Network-based systems don't require cooperation from the clients, and try to fix security by parsing traffic. Some network-based systems require a little bit of cooperation by blocking encrypted traffic for connections that don't submit to scrutiny; and accept the company/ISP's certificate authority (so that the authority at the local boundary can inspect the traffic).
Proxy, Adaptable Security Appliance, DMZ, and Automated Vulnerability Scanners are some items you'll find in the wild that are hardware. There's plenty more security related software items that will help you with research such as Splunk which takes logs and makes them searchable.