As you have asked about the exams for jobs in Railways, check below for the information
The Indian railways are generally divided and sub-divided into zones, divisions and departments, each controlling a particular function.
Every division has a definite number of technical and non-technical departments, which form the base organization on which the railways function.
Technical departments comprise civil, technical and mechanical engineering, signalling and telecom, and several others dealing with similar disciplines
The highest are the Group A officers, while the lowest in rank are the Group D staff members.
Group A:
UPSC SCRA Exam:
Group A officers are hired by UPSC
Civil Service Examination:
Indian Railway Traffic Service (IRTS) and the Indian Railways Accounts Service (IRAS)
Combined Engineering Service:
Indian Railway Service of Engineers ( IRSE ), Indian Railway Service of Electrical Engineers (IRSEE), Indian Railway Services of Signal Engineers ( IRSSE ) and Indian Railway Store Service (IRSS)

Group B:
Group B officers are directly promoted from Group C.

Group C
Group C officers are recruited through the Railway Recruitment Board ( RRB).
The Group C posts include assistant station masters, drivers, motormen, guards, signal and mechanical inspectors. Here again, staff are divided into technical and non-technical staff.

Technical Cadre Examination
Indian Railway Technical Cadre Exam Non-Technical Cadre Examination
Indian Railway Non-Technical Cadre
RPF Sub-Inspectors / Constables Examination